Antibiotic-associated haemorrhagic colitis is an uncommon cause of bloody d
iarrhoea in patients taking penicillin or penicillin-related antibiotics. S
ymptoms of abdominal pain and bloody diarrhoea occur within 1 week of antib
iotic use and resolve without specific therapy within days of discontinuing
the offending antibiotic. There is an apparent increased incidence of the
disease in patients of Oriental ethnicity. The pathogenesis is unknown. We
present two cases of haemorrhagic colitis in patients taking penicillin-rel
ated antibiotics who presented within 4 months of each other. One of the pa
tients was being treated for Helicobacter pylori infection. The published l
iterature is reviewed with particular emphasis on the histology and pathoge
nesis of the condition.