China 
Africa 
- Arenavirus
- Arene oxide
- Areola
- Arformoterol
- Argan oil
- Argasidae
- Argatroban
- Argemone mexicana
- Argentine hemorrhagic fever
- Arginase
- Arginine
- Arginine catabolic mobile element
- Arginine decarboxylase
- Arginine deiminase
- Arginine glutamate
- Arginine kinase
- Arginine vasopressin
- Arginine vasopressin receptor 2
- Argininemia
- Argininosuccinate lyase
- Argininosuccinate synthase
- Argininosuccinic acid
- Argininosuccinic aciduria
- Arginylation
- Arginylglycylaspartic acid
- Argon
- Argon plasma coagulation
- Argyll Robertson pupil
- Argyreia nervosa
- Argyria
- Arias-Stella reaction
- Aripiprazole
- Aristolochia
- Aristolochia clematitis
- Aristolochic acid
- Arm
- Arm bone
- Arm span
- Armed Forces Radiobiology Research Institute
- Armodafinil
- Armrest
- Army Alpha
- Arnica
- Arnica montana
- Arnold Chiari Malformation
- Arnold-Chiari malformation
- Aroclor
- Aroma
- Aroma compounds
- Aromadendrin
- Aromatase
- Aromatase deficiency
- Aromatase inhibitors
- Aromatherapy
- Aromatic L-amino acid decarboxylase
- Aromatic amines
- Aromatic amino acids
- Aromatic compounds
- Aromatic hydrocarbons
- Aromatic l-amino acid decarboxylase
- Aromatic l-amino acid decarboxylase inhibitor
- Aromatic rings
- Aromaticity
- Aromatics
- Aromatization
- Arp2/3 complex
- Arq197
- Array comparative genomic hybridization
- Arrector pili
- Arrestin
- Arrhythmia
- Arrhythmias
- Arrow poison
- Arrowroot
- Arsanilic acid
- Arsenic
- Arsenic poisoning
- Arsenic toxicity
- Arsenic trioxide
- Arsenical
- Arsenical keratosis
- Arsenide
- Arsenite
- Arsenobetaine
- Arsine
- Arsphenamine
- Art therapy
- Arteether
- Artefill
- Artemether
- Artemin
- Artemisia
- Artemisia abrotanum
- Artemisia absinthium
- Artemisia annua
- Artemisia argyi
- Artemisia dracunculus
- Artemisia herba-alba
- Artemisia maritima
- Artemisia scoparia
- Artemisia vulgaris
- Artemisinin
- Arterial blood
- Arterial blood gas
- Arterial cannula
- Arterial catheter
- Arterial circulation
- Arterial embolism
- Arterial embolization
- Arterial input function
- Arterial insufficiency
- Arterial line
- Arterial occlusion
- Arterial oxygen saturation
- Arterial oxygen tension
- Arterial pressure
- Arterial spin labeling
- Arterial stiffness
- Arterial switch operation
- Arterial thromboembolism
- Arterial thrombosis
- Arterial tortuosity syndrome
- Arterial tree
- Arteries
- Arteriogenesis
- Arteriography
- Arteriolar vasodilator
- Arterioles
- Arteriolosclerosis
- Arteriosclerosis
- Arteriosclerosis obliterans
- Arteriotomy
- Arteriovenous anastomosis
- Arteriovenous fistula
- Arteriovenous malformations
- Arteriovenous nicking
- Arteriovenous oxygen difference
- Arteriovenous shunt
- Arteritis
- Arteriviridae
- Arterivirus
- Arterolane
- Artery
- Artery disease
- Artery of Percheron
- Artery spasm
- Artery wall
- Artesunate
- Arthralgia
- Arthritis