The objective of this study was to evaluate risk factors for death due to diarrhoea among hospitalized children at the Aga Khan University Hospital (AKUH), Karachi. We conducted a retrospective case-control study of all diarrhoea deaths at AKUH over the period 1988-93. For each death, the next two consecutive admissions matched for gender and type of diarrhoea were identified as controls. Data were analysed by univariate methods and logistic regression analysis. A total of 42 deaths and 84 matched controls were identified. Blood cultures at admission were obtained in all deaths and 94% of controls. The rates of isolation of organisms from blood cultures were significantly higher among deaths [38 versus 9%, odds ratio (OR) 6.5, 95% confidence interval (CI) 2.2-19.9], the majority of which were Gram-negative Enterobacteriaceae (94 versus 57%, Fisher's exact test p < 0.02). Conditional logistic regression revealed that several clinical and laboratory features of systemic infection were associated with a significantly increased risk of mortality, such as anorexia (OR 3.9, 95% CI 1.4-10.9), drowsiness (OR 4.4, 95% CI 1.3-15.3), respiratory distress (OR 7.0, 95% CI 1.4 36.6), anaemia (OR 5.8, 95% CI 2.0-16.6) and a positive blood culture (OR 8.7, 95% CI 2.5-30.7). Our data suggest that bacteraemia with Enterobacteriaceae is common among hospitalized malnourished children with diarrhoea and systemic infection may be an important risk factor for mortality.