| 1. | Narcolepsy (3 recruiting studies) |
| 2. | Nasopharyngeal Carcinoma (46 recruiting studies) |
| 3. | Nasopharyngeal Diseases (13 recruiting studies) |
| 4. | Nasopharyngeal Neoplasms (13 recruiting studies) |
| 5. | Nausea (9 recruiting studies) |
| 6. | Nearsightedness (1 recruiting study) |
| 7. | Neck Injuries (1 recruiting study) |
| 8. | Neck Pain (4 recruiting studies) |
| 9. | Necrosis (3 recruiting studies) |
| 10. | Nematode Infections (2 recruiting studies) |
| 11. | Neoplasm Metastasis (280 recruiting studies) |
| 12. | Neoplasm Recurrence, Local (1 recruiting study) |
| 13. | Neoplasms (2357 recruiting studies) |
| 14. | Neoplasms by Histologic Type (1236 recruiting studies) |
| 15. | Neoplasms by Site (1282 recruiting studies) |
| 16. | Neoplasms, Adipose Tissue (2 recruiting studies) |
| 17. | Neoplasms, Basal Cell (6 recruiting studies) |
| 18. | Neoplasms, Bone Tissue (28 recruiting studies) |
| 19. | Neoplasms, Complex and Mixed (6 recruiting studies) |
| 20. | Neoplasms, Connective and Soft Tissue (90 recruiting studies) |
| 21. | Neoplasms, Connective Tissue (40 recruiting studies) |
| 22. | Neoplasms, Ductal, Lobular, and Medullary (4 recruiting studies) |
| 23. | Neoplasms, Experimental (18 recruiting studies) |
| 24. | Neoplasms, Fibroepithelial (1 recruiting study) |
| 25. | Neoplasms, Fibrous Tissue (5 recruiting studies) |
| 26. | Neoplasms, Germ Cell and Embryonal (309 recruiting studies) |
| 27. | Neoplasms, Glandular and Epithelial (493 recruiting studies) |
| 28. | Neoplasms, Hormone-Dependent (1 recruiting study) |
| 29. | Neoplasms, Mesothelial (13 recruiting studies) |
| 30. | Neoplasms, Multiple Primary (1 recruiting study) |
| 31. | Neoplasms, Muscle Tissue (25 recruiting studies) |
| 32. | Neoplasms, Nerve Tissue (302 recruiting studies) |
| 33. | Neoplasms, Neuroepithelial (156 recruiting studies) |
| 34. | Neoplasms, Squamous Cell (10 recruiting studies) |
| 35. | Neoplasms, Unknown Primary (5 recruiting studies) |
| 36. | Neoplasms, Vascular Tissue (17 recruiting studies) |
| 37. | Neoplastic Endocrine-Like Syndromes (5 recruiting studies) |
| 38. | Neoplastic Processes (123 recruiting studies) |
| 39. | Neoplastic Syndromes, Hereditary (19 recruiting studies) |
| 40. | Neovascularization, Pathologic (6 recruiting studies) |
| 41. | Nephritis (11 recruiting studies) |
| 42. | Nephroblastoma (14 recruiting studies) |
| 43. | Nephrosis (11 recruiting studies) |
| 44. | Nephrosis, Lipoid (1 recruiting study) |
| 45. | Nephrotic Syndrome (3 recruiting studies) |
| 46. | Nerve Compression Syndromes (2 recruiting studies) |
| 47. | Nerve Degeneration (3 recruiting studies) |
| 48. | Nerve Sheath Tumors (6 recruiting studies) |
| 49. | Nervous System Diseases (567 recruiting studies) |
| 50. | Nervous System Malformations (8 recruiting studies) |
| 51. | Nervous System Neoplasms (105 recruiting studies) |
| 52. | Neural Tube Defects (5 recruiting studies) |
| 53. | Neuralgia (4 recruiting studies) |
| 54. | Neurilemmoma (2 recruiting studies) |
| 55. | Neuritis (1 recruiting study) |
| 56. | Neurobehavioral Manifestations (36 recruiting studies) |
| 57. | Neuroblastoma (59 recruiting studies) |
| 58. | Neurocutaneous Syndromes (16 recruiting studies) |
| 59. | Neurodegenerative Diseases (125 recruiting studies) |
| 60. | Neuroectodermal Tumors (309 recruiting studies) |
| 61. | Neuroectodermal Tumors, Primitive (68 recruiting studies) |
| 62. | Neuroectodermal Tumors, Primitive, Peripheral (41 recruiting studies) |
| 63. | Neuroendocrine Tumors (141 recruiting studies) |
| 64. | Neurofibroma (6 recruiting studies) |
| 65. | Neurofibroma, Plexiform (3 recruiting studies) |
| 66. | Neurofibromatoses (7 recruiting studies) |
| 67. | Neurofibromatosis 1 (4 recruiting studies) |
| 68. | Neurofibromatosis 2 (3 recruiting studies) |
| 69. | Neurofibrosarcoma (10 recruiting studies) |
| 70. | Neurologic Manifestations (122 recruiting studies) |
| 71. | Neuroma (2 recruiting studies) |
| 72. | Neuroma, Acoustic (2 recruiting studies) |
| 73. | Neuromuscular Diseases (67 recruiting studies) |
| 74. | Neuromuscular Junction Diseases (2 recruiting studies) |
| 75. | Neuromuscular Manifestations (4 recruiting studies) |
| 76. | Neuronal Ceroid-Lipofuscinosis (1 recruiting study) |
| 77. | Neurotoxicity Syndromes (11 recruiting studies) |
| 78. | Neutropenia (22 recruiting studies) |
| 79. | Nevi and Melanomas (91 recruiting studies) |
| 80. | Nevus (93 recruiting studies) |
| 81. | Nevus, Pigmented (91 recruiting studies) |
| 82. | Nidovirales Infections (1 recruiting study) |
| 83. | Niemann-Pick Diseases (1 recruiting study) |
| 84. | Non-Alcoholic Steatohepatitis (3 recruiting studies) |
| 85. | Nonsyndromic Hereditary Hearing Impairment (1 recruiting study) |
| 86. | Nose Diseases (8 recruiting studies) |
| 87. | Nose Neoplasms (6 recruiting studies) |
| 88. | Nutrition Disorders (38 recruiting studies) |
| 89. | Nutritional and Metabolic Diseases (182 recruiting studies) |
| 90. | Nystagmus, Pathologic (2 recruiting studies) |
