The objective of our analysis was to describe the aetiology, clinical features, and socio-demographic background of adults with diarrhoea attending different urban and rural diarrhoeal disease hospitals in Bangladesh. Between January 2010 and December 2011, a total of 5054 adult diarrhoeal patients aged ⩾20 years were enrolled into the Diarrhoeal Disease Surveillance Systems at four different hospitals (two rural and two urban) of Bangladesh. Middle-aged [adjusted odds ratio (aOR) 0·28, 95% confidence interval (CI) 0·23–0·35, P < 0·001] and elderly (aOR 0·15, 95% CI 0·11–0·20, P < 0·001) patients were more likely to present to rural diarrhoeal disease facilities than urban ones. Vibrio cholerae was the most commonly isolated pathogen (16%) of the four pathogens tested followed by rotavirus (5%), enterotoxigenic Escherichia coli (ETEC) (4%), and Shigella (4%). Of these pathogens, V. cholerae (19% vs. 11%, P < 0·001), ETEC (9% vs. 4%, P < 0·001), and rotavirus (5% vs. 3%, P = 0·013) were more commonly detected from patients presenting to urban hospitals than rural hospitals, but Shigella was more frequently isolated from patients presenting to rural hospitals than urban hospitals (7% vs. 2%, P < 0·001). The isolation rate of Shigella was higher in the elderly than in younger adults (8% vs. 3%, P < 0·001). Some or severe dehydration was higher in urban adults than rural adults (P < 0·001). Our findings indicate that despite economic and other progress made, conditions facilitating transmission of V. cholerae and Shigella prevail in adults with diarrhoea in Bangladesh and further efforts are needed to control these infections.