There is limited information on percent expenditure of household income due to childhood diarrhoea especially in rural Bangladesh. A total of 4205 children aged <5 years with acute diarrhoea were studied. Percent expenditure was calculated as total expenditure for the diarrhoeal episode divided by monthly family income, multiplied by 100. Overall median percent expenditure was 3·04 (range 0·01–94·35). For Vibrio cholerae it was 6·42 (range 0·52–82·85), for enterotoxigenic Escherichia coli 3·10 (range 0·22–91·87), for Shigella 3·17 (range 0·06–77·80), and for rotavirus 3·08 (range 0·06–48·00). In a multinomial logistic regression model, for the upper tertile of percent expenditure, significant higher odds were found for male sex, travelling a longer distance to reach hospital (⩾median of 4 miles), seeking care elsewhere before attending hospital, vomiting, higher frequency of purging (⩾10 times/day), some or severe dehydration and stunting. V. cholerae was the highest and rotavirus was the least responsible pathogen for percent expenditure of household income due to childhood diarrhoea.