Respiratory and gastrointestinal infections are the top killers of children worldwide, and their co-occurrence is reported but not well understood. Our aim was to determine the risk factors for concurrent presentation of diarrhea and pneumonia (DP) in a resource-limited setting in Bangladesh. We used data from the Diarrheal Disease Surveillance System of the icddr,b Dhaka Hospital to identify children < 60 months of age with diarrhea and concurrent pneumonia, defined as a history of cough, an abnormal lung examination, and tachypnea. For the years 1996-2007, out of total 14,628 diarrheal patients surveyed, there were 607 (4%) patients who satisfied criteria for pneumonia. Those with DP had a higher mortality rate (4% versus 0.05%, odds ratio [OR] = 86, 95% confidence interval [CI] = 26-286) and a longer hospital stay (mean 84 versus 26 hours, difference 58 hours, 95% CI = 52-64 hours) than those with diarrhea (D) only. In multivariable logistic regression comparing cases (N = 607) with controls matched for month and year of admission at a ratio of 1:3 (N = 1,808), we found that DP was associated with younger age, male gender, severe acute malnutrition (SAM), less maternal education, lower family income, and lack of current breast-feeding history.