A cross-sectional hospital-based study was carried out at Tikrit teaching hospital, Iraq, from October 2004 to September 2005, to identify the prevalence and etiology of nosocomial infectious diarrhoea among children under 5 years of age. Of 259 children admitted to the paediatric ward for reasons other than diarrhoea and hospitalized for more than 3 days, clinical and laboratory analysis of stool samples showed nosocomial diarrhoea in 84 children (32.4%). The most common causative agents were enteropathogenic Escherichia coli (25.9%), Clostridium difficile (21.0%) and rotavirus (18.5%). Single infectious agents caused 63.1% of the cases, while mixed infections were detected in 16.7%; in 20.2% of children the cause remained unknown.