| 1. | Salivary Gland Diseases (12 recruiting studies) |
| 2. | Salivary Gland Neoplasms (7 recruiting studies) |
| 3. | Sarcodina Infections (1 recruiting study) |
| 4. | Sarcoidosis (3 recruiting studies) |
| 5. | Sarcoma (102 recruiting studies) |
| 6. | Sarcoma, Alveolar Soft Part (4 recruiting studies) |
| 7. | Sarcoma, Clear Cell (2 recruiting studies) |
| 8. | Sarcoma, Ewing's (34 recruiting studies) |
| 9. | Sarcoma, Kaposi (15 recruiting studies) |
| 10. | Sarcoma, Synovial (12 recruiting studies) |
| 11. | Sarcomastigophora Infections (2 recruiting studies) |
| 12. | Schizophrenia (71 recruiting studies) |
| 13. | Schizophrenia and Disorders with Psychotic Features (68 recruiting studies) |
| 14. | Schizophrenia, Childhood (1 recruiting study) |
| 15. | Sciatic Neuropathy (2 recruiting studies) |
| 16. | Sciatica (2 recruiting studies) |
| 17. | Scleral Diseases (1 recruiting study) |
| 18. | Scleritis (1 recruiting study) |
| 19. | Scleroderma, Localized (3 recruiting studies) |
| 20. | Scleroderma, Systemic (7 recruiting studies) |
| 21. | Sclerosis (46 recruiting studies) |
| 22. | Scoliosis (1 recruiting study) |
| 23. | Seasonal Affective Disorder (2 recruiting studies) |
| 24. | Secernentea Infections (2 recruiting studies) |
| 25. | Secondary Acute Myeloid Leukemia (49 recruiting studies) |
| 26. | Seizures (19 recruiting studies) |
| 27. | Self-Injurious Behavior (2 recruiting studies) |
| 28. | Seminoma (9 recruiting studies) |
| 29. | Sensation Disorders (14 recruiting studies) |
| 30. | Sepsis (16 recruiting studies) |
| 31. | Sepsis Syndrome (2 recruiting studies) |
| 32. | Septicemia (16 recruiting studies) |
| 33. | Serotonin Syndrome (6 recruiting studies) |
| 34. | Severe Acute Respiratory Syndrome (2 recruiting studies) |
| 35. | Severe Combined Immunodeficiency (7 recruiting studies) |
| 36. | Sex Chromosome Disorders (3 recruiting studies) |
| 37. | Sex Differentiation Disorders (3 recruiting studies) |
| 38. | Sex Disorders (2 recruiting studies) |
| 39. | Sexual and Gender Disorders (1 recruiting study) |
| 40. | Sexual Dysfunctions, Psychological (1 recruiting study) |
| 41. | Sexually Transmitted Diseases (222 recruiting studies) |
| 42. | Sexually Transmitted Diseases, Bacterial (1 recruiting study) |
| 43. | Sexually Transmitted Diseases, Viral (220 recruiting studies) |
| 44. | Sezary Syndrome (50 recruiting studies) |
| 45. | Shock (7 recruiting studies) |
| 46. | Shock, Cardiogenic (1 recruiting study) |
| 47. | Shock, Hemorrhagic (1 recruiting study) |
| 48. | Shock, Septic (4 recruiting studies) |
| 49. | Short Bowel Syndrome (2 recruiting studies) |
| 50. | Shoulder Pain (1 recruiting study) |
| 51. | Shprintzen Syndrome (1 recruiting study) |
| 52. | Shwachman Syndrome (2 recruiting studies) |
| 53. | Shy-Drager Syndrome (1 recruiting study) |
| 54. | Sickle Cell Trait (1 recruiting study) |
| 55. | Sigmoid Diseases (2 recruiting studies) |
| 56. | Sigmoid Neoplasms (2 recruiting studies) |
| 57. | Signs and Symptoms (387 recruiting studies) |
| 58. | Signs and Symptoms, Digestive (25 recruiting studies) |
| 59. | Signs and Symptoms, Respiratory (3 recruiting studies) |
| 60. | Sitosterolemia (1 recruiting study) |
| 61. | Sjogren's Syndrome (4 recruiting studies) |
| 62. | Skin Abnormalities (3 recruiting studies) |
| 63. | Skin and Connective Tissue Diseases (140 recruiting studies) |
| 64. | Skin Diseases (83 recruiting studies) |
| 65. | Skin Diseases, Bacterial (5 recruiting studies) |
| 66. | Skin Diseases, Genetic (4 recruiting studies) |
| 67. | Skin Diseases, Infectious (12 recruiting studies) |
| 68. | Skin Diseases, Metabolic (6 recruiting studies) |
| 69. | Skin Diseases, Papulosquamous (8 recruiting studies) |
| 70. | Skin Diseases, Vascular (4 recruiting studies) |
| 71. | Skin Diseases, Vesiculobullous (1 recruiting study) |
| 72. | Skin Diseases, Viral (6 recruiting studies) |
| 73. | Skin Manifestations (2 recruiting studies) |
| 74. | Skin Neoplasms (12 recruiting studies) |
| 75. | Skin Ulcer (6 recruiting studies) |
| 76. | Skull Neoplasms (6 recruiting studies) |
| 77. | Sleep Apnea Syndromes (10 recruiting studies) |
| 78. | Sleep Apnea, Obstructive (5 recruiting studies) |
| 79. | Sleep Deprivation (4 recruiting studies) |
| 80. | Sleep Disorders (21 recruiting studies) |
| 81. | Sleep Disorders, Circadian Rhythm (2 recruiting studies) |
| 82. | Sleep Disorders, Intrinsic (19 recruiting studies) |
| 83. | Sleep Initiation and Maintenance Disorders (5 recruiting studies) |
| 84. | Slow Virus Diseases (11 recruiting studies) |
| 85. | Smallpox (3 recruiting studies) |
| 86. | Smith-Lemli-Opitz Syndrome (5 recruiting studies) |
| 87. | Smith-Magenis Syndrome (1 recruiting study) |
| 88. | Smoking (17 recruiting studies) |
| 89. | Soft Tissue Infections (1 recruiting study) |
| 90. | Soft Tissue Neoplasms (8 recruiting studies) |
| 91. | Somatoform Disorders (1 recruiting study) |
| 92. | Somatosensory Disorders (2 recruiting studies) |
| 93. | Somatostatinoma (3 recruiting studies) |
| 94. | Spasm (1 recruiting study) |
| 95. | Spasmodic Dysphonia (6 recruiting studies) |
| 96. | Spastic Dysphonia (6 recruiting studies) |
| 97. | Speech Disorders (8 recruiting studies) |
| 98. | Sphingolipidoses (14 recruiting studies) |
| 99. | Spinal Cord Diseases (33 recruiting studies) |
| 100. | Spinal Cord Injuries (10 recruiting studies) |
| 101. | Spinal Cord Neoplasms (7 recruiting studies) |
| 102. | Spinal Diseases (11 recruiting studies) |
| 103. | Spinal Dysraphism (2 recruiting studies) |
| 104. | Spinal Fractures (1 recruiting study) |
| 105. | Spinal Injuries (1 recruiting study) |
| 106. | Spinal Stenosis (3 recruiting studies) |
| 107. | Spinocerebellar Degenerations (4 recruiting studies) |
| 108. | Spirochaetales Infections (4 recruiting studies) |
| 109. | Spirurida Infections (1 recruiting study) |
| 110. | Splenic Diseases (2 recruiting studies) |
| 111. | Splenomegaly (1 recruiting study) |
| 112. | Spondylarthritis (8 recruiting studies) |
| 113. | Spondylarthropathies (8 recruiting studies) |
| 114. | Spondylitis (5 recruiting studies) |
| 115. | Spondylitis, Ankylosing (5 recruiting studies) |
| 116. | Spondylolisthesis (2 recruiting studies) |
| 117. | Sprains and Strains (3 recruiting studies) |
| 118. | Staphylococcal Infections (5 recruiting studies) |
| 119. | Staphylococcal Skin Infections (2 recruiting studies) |
| 120. | Stargardt's Disease (2 recruiting studies) |
| 121. | Stereotypic Movement Disorder (1 recruiting study) |
| 122. | Stiff-Person Syndrome (2 recruiting studies) |
| 123. | Stomach Diseases (31 recruiting studies) |
| 124. | Stomach Neoplasms (26 recruiting studies) |
| 125. | Stomatitis (2 recruiting studies) |
| 126. | Stomatitis, Aphthous (1 recruiting study) |
| 127. | Stomatognathic Diseases (66 recruiting studies) |
| 128. | Stomatognathic System Abnormalities (3 recruiting studies) |
| 129. | Strabismus (3 recruiting studies) |
| 130. | Streptococcal Infections (1 recruiting study) |
| 131. | Stress (37 recruiting studies) |
| 132. | Stress Disorders, Post-Traumatic (18 recruiting studies) |
| 133. | Stress Disorders, Traumatic (18 recruiting studies) |
| 134. | Stress Disorders, Traumatic, Acute (1 recruiting study) |
| 135. | Strongyloidiasis (1 recruiting study) |
| 136. | Sturge-Weber Syndrome (16 recruiting studies) |
| 137. | Stuttering (6 recruiting studies) |
| 138. | Subarachnoid Hemorrhage (2 recruiting studies) |
| 139. | Substance Abuse, Intravenous (2 recruiting studies) |
| 140. | Substance-Related Disorders (63 recruiting studies) |
| 141. | Suicide (4 recruiting studies) |
| 142. | Suicide, Attempted (2 recruiting studies) |
| 143. | Suppuration (2 recruiting studies) |
| 144. | Supranuclear Palsy, Progressive (2 recruiting studies) |
| 145. | Supratentorial Neoplasms (4 recruiting studies) |
| 146. | Surgical Wound Infection (1 recruiting study) |
| 147. | Syncope (1 recruiting study) |
| 148. | Syndactyly (1 recruiting study) |
| 149. | Syndrome X (1 recruiting study) |
| 150. | Synostosis (2 recruiting studies) |
| 151. | Synovitis (1 recruiting study) |
| 152. | Syphilis (1 recruiting study) |
| 153. | Syringomyelia (3 recruiting studies) |
