During the 2 years of the study, 402 patients and an equal number of age- and sex-matched controls were investigated for the presence of diarrhoeal pathogens. Pathogenic organisms were recovered from 277 (68.9%) patients and 97 (24.1%) controls. In the patient group, possible bacterial pathogens were found in 210 (52.2%) cases. Enteropathogenic Escherichia coli (EPEC) was the most frequently found potential pathogen, being recovered in 132 cases (32.8%) with serotypes 026, 086, 0111 and 0124 being the most frequently identified. Other bacterial pathogens identified were enterotoxigenic E. coli (ETEC) 57 (14.2%), Shigella 13 (3.2%) and Salmonella eight (2%). Rotavirus was identified in 33 (8.2%) cases. Mixed bacterial and viral infections were also seen in 26 (6.5%) cases. In the control group, enteric pathogens were recovered from 97 (24.1%) specimens. The most common bacterial pathogen found in this group was again EPEC (40, 9.9%), with serogroups 018, 044, 0111 and 0126 being the most frequent. Giardia lamblia and Entamoeba histolytica were found in 31 (7.7%) and 10 (2.5%) controls, respectively. Rotavirus was found in 16 (4%) controls. The results of both centres where the study was performed (Karachi and Rawalpindi) were compared.