This study was carried out on 1600 rectal swabs from children under 5 years of age admitted at the health centre in Islamshahr, Tehran province, Islamic Republic of Iran, during 1998-99. The specimens were examined for various bacterial pathogens. Isolation rates were: enteropathogenic Escherichia coli 6.8%, Shigella spp. 3.4%, Salmonella spp. 2.9%, Campylobacter spp. 0.9%, Yersinia spp. 0.7%. The isolation rate was highest in the summer, except for Yersinia spp., which was predominantly isolated in spring. The results of this study demonstrate the significance of Yersinia spp. and Campylobacter spp. in patients with diarrhoea.