To determine the causes of gastroenteritis at a major referral centre in Saudi Arabia, retrospective study was carried out on 58,110 fresh stools from 42,035 patients. Examination of stool specimens for pathogens was based on the clinical judgement of the physician responsible, so that all specimens were not tested for the presence of all pathogen groups. Bacterial enteropathogens were found in 7.7% of patients; Salmonella species (51.7%) were found to be the most frequent pathogens followed by Compylobacter jejuni (28%) and Shigella species (14.9%). Protozoan or metazoan parasites were detected in 27.8% of patients examined, the most common being Giardia lamblia and Hymenolepsis nana. Of the patients tested for viruses in stool, 14.1% had rotavirus, 5.3% adenovirus, 1.2% small round viruses and 0.3% coronavirus. Clostridium difficile toxin was also found in 9.5% of patients examined.