The objective was to determine the prevalence of parasitic agents among under-five children with diarrhea in Ilesa, Nigeria and the clinical correlates of diarrhea associated with parasitic infestation. All under-five children presenting with diarrhea in the hospital had stool microscopic examination. Children with parasites in diarrheic stools (cases) were compared with those without (controls) for clinical features. Out of 300 under-five children with diarrhea, 70 (23.3%) had parasites. There were 18 (6%) helminthes and 52 (17.3%) protozoas. These included the ova ofAscaris lumbricoides (13; 18.6%), cysts and trophozoites ofEntamoeba. histolytica (46; 65.7%), cysts ofEntamoeba coli (1; 1.4%),Giardia Lamblia (5; 7.1%),Necator american us (1; 1.4%) andTrichuris trichiuria (4; 5.7%). As against the controls, the cases were older (t=4.88; p=0:0000017), more undernourished (OR=2.04; 95% Cl=1.14 to 3.63; p=0.009) and belonged to the lower socio-economic classes (OR=7.15; 95% Cl=3.83 to 13.43; p=0.0000). It is concluded that parasitic infestations are commonly associated with childhood diarrhoea in Nigeria. Malnutrition and low socio-conomic status are risk factors.