Duodenal villous atrophy with olmesartan was described in 2012, 10 years following registration of olmesartan. Clinical features are severe watery diarrhoea, usually occurring in association with weight loss. Onset is delayed, with a mean duration of prior exposure to olmesartan of 3 years. Diagnosis may be delayed. Symptoms resolve over weeks following cessation of olmesartan. Epidemiological studies suggest increased risk with olmesartan, rather than a class effect of all angiotensin receptor blockers. Postmarketing surveillance for drug safety remains important.