- Abscess of lung
- Abscess of lung with pneumonia
- Acanthosis nigricans
- Acne
- Actinomycosis
- Active bleeding
- Acute appendicitis
- Acute bronchiolitis
- Acute bronchitis
- Acute hepatitis A
- Acute hepatitis B
- Acute hepatitis C
- Acute laryngitis
- Acute myocardial infarction
- Acute myocarditis
- Acute nasopharyngitis (common cold)
- Acute obstructive laryngitis (croup)
- Acute pericarditis
- Acute pharyngitis
- Acute poliomyelitis
- Acute sinusitis
- Acute stress reaction
- Acute & subacute endocarditis
- Acute tonsillitis
- Adult osteomalacia
- African trypanosomiasis
- Agoraphobia
- Albinism
- Alcoholic cirrhosis of liver
- Alcoholic hepatitis
- Alcoholic liver disease
- Allergic contact dermatitis
- Allergic rhinitis (hay fever)
- Allergy
- Alzheimer's disease
- Amenorrhoea
- Amoebiasis
- Anaemia
- Anal cancer
- Anal fissure
- Anal fistula
- Angina pectoris
- Annovulation
- Anogenital herpes viral infection
- Anogenital (venereal) warts
- Anorexia nervosa
- Anthrax
- Anxiety hysteria
- Arrhythmia
- Arthritis
- Arthropathy
- Ascariasis
- Ascorbic acid deficiency
- Aspergillosis
- Asthma
- Atopic dermatitis
- Atrial fibrillation
- Atrial flutter
- Atrial septal defect
- Atrophy and hypertrophy of vulva