| 1. | Bacillaceae Infections (2 recruiting studies) |
| 2. | Back Injuries (1 recruiting study) |
| 3. | Back Pain (8 recruiting studies) |
| 4. | Bacteremia (5 recruiting studies) |
| 5. | Bacterial Infections (80 recruiting studies) |
| 6. | Bacterial Infections and Mycoses (80 recruiting studies) |
| 7. | Bacteriuria (1 recruiting study) |
| 8. | Bardet-Biedl Syndrome (1 recruiting study) |
| 9. | Barrett Esophagus (1 recruiting study) |
| 10. | Basal Ganglia Diseases (46 recruiting studies) |
| 11. | Behavior (143 recruiting studies) |
| 12. | Behavior and Behavior Mechanisms (105 recruiting studies) |
| 13. | Behavior, Addictive (3 recruiting studies) |
| 14. | Behavioral Symptoms (72 recruiting studies) |
| 15. | Behcet Syndrome (1 recruiting study) |
| 16. | Benign Essential Tremor Syndrome (4 recruiting studies) |
| 17. | beta-Thalassemia (6 recruiting studies) |
| 18. | Bifunctional Enzyme Deficiency (1 recruiting study) |
| 19. | Bile Duct Diseases (12 recruiting studies) |
| 20. | Bile Duct Neoplasms (7 recruiting studies) |
| 21. | Biliary Atresia (1 recruiting study) |
| 22. | Biliary Tract Diseases (13 recruiting studies) |
| 23. | Biliary Tract Neoplasms (8 recruiting studies) |
| 24. | Bipolar Disorder (36 recruiting studies) |
| 25. | Bladder Diseases (41 recruiting studies) |
| 26. | Bladder Neoplasms (40 recruiting studies) |
| 27. | Blast Crisis (3 recruiting studies) |
| 28. | Blastomycosis (1 recruiting study) |
| 29. | Blepharitis (1 recruiting study) |
| 30. | Blepharospasm (1 recruiting study) |
| 31. | Blindness (4 recruiting studies) |
| 32. | Blister (1 recruiting study) |
| 33. | Blood Coagulation Disorders (77 recruiting studies) |
| 34. | Blood Coagulation Disorders, Inherited (5 recruiting studies) |
| 35. | Blood Platelet Disorders (13 recruiting studies) |
| 36. | Blood Protein Disorders (60 recruiting studies) |
| 37. | Body Temperature Changes (2 recruiting studies) |
| 38. | Body Weight Changes (42 recruiting studies) |
| 39. | Bone Diseases (95 recruiting studies) |
| 40. | Bone Diseases, Developmental (14 recruiting studies) |
| 41. | Bone Diseases, Endocrine (5 recruiting studies) |
| 42. | Bone Diseases, Infectious (1 recruiting study) |
| 43. | Bone Diseases, Metabolic (45 recruiting studies) |
| 44. | Bone Marrow Diseases (150 recruiting studies) |
| 45. | Bone Neoplasms (15 recruiting studies) |
| 46. | Bone Resorption (3 recruiting studies) |
| 47. | Borderline Personality Disorder (3 recruiting studies) |
| 48. | Borrelia Infections (3 recruiting studies) |
| 49. | Botulism (1 recruiting study) |
| 50. | Brain Concussion (1 recruiting study) |
| 51. | Brain Damage, Chronic (6 recruiting studies) |
| 52. | Brain Diseases (305 recruiting studies) |
| 53. | Brain Diseases, Metabolic (19 recruiting studies) |
| 54. | Brain Diseases, Metabolic, Inborn (19 recruiting studies) |
| 55. | Brain Edema (2 recruiting studies) |
| 56. | Brain Infarction (1 recruiting study) |
| 57. | Brain Injuries (19 recruiting studies) |
| 58. | Brain Ischemia (5 recruiting studies) |
| 59. | Brain Neoplasms (128 recruiting studies) |
| 60. | Brain Stem Neoplasms (1 recruiting study) |
| 61. | Breast Diseases (256 recruiting studies) |
| 62. | Breast Neoplasms (256 recruiting studies) |
| 63. | Breast Neoplasms, Male (23 recruiting studies) |
| 64. | Brenner Tumor (6 recruiting studies) |
| 65. | Bronchial Diseases (137 recruiting studies) |
| 66. | Bronchial Neoplasms (107 recruiting studies) |
| 67. | Bronchiectasis (1 recruiting study) |
| 68. | Bronchiolitis (2 recruiting studies) |
| 69. | Bronchiolitis Obliterans (1 recruiting study) |
| 70. | Bronchitis (4 recruiting studies) |
| 71. | Bronchitis, Chronic (1 recruiting study) |
| 72. | Bronchopulmonary Dysplasia (2 recruiting studies) |
| 73. | Brown-Sequard Syndrome (1 recruiting study) |
| 74. | Brucellosis (1 recruiting study) |
| 75. | Bulimia (2 recruiting studies) |
| 76. | Burkitt Lymphoma (88 recruiting studies) |
| 77. | Burning Mouth Syndrome (1 recruiting study) |
| 78. | Burns (2 recruiting studies) |
