The enteric protozoa, Cryptosporidium, Giardia and Entamoeba histolytica, cause diarrhea in children. We investigated the association of enteric protozoan-associated diarrheal illness with the nutritional status and growth of preschool children in Dhaka, Bangladesh. The subjects were 221 children aged 2-5 years who were followed prospectively for diarrheal illness for 3 years. The weight and height of the children were measured at entry and at 4-month intervals. Cryptosporidium and E. histolytica were diagnosed with commercially available stool antigen detection kits. Giardia was diagnosed by conventional microscopy. Cryptosporidium- and Giardia-associated diarrheal illness was not associated with the growth of the children. Children with E. histolytica-associated diarrheal illness had lower weight for age Z-score changes (-0.103+/-0.120 vs. 0.176+/-0.052, P=0.038). Similarly, the change in height for age Z-score was lower in children with E. histolytica-associated diarrheal illness (-0.348+/-0.186 vs. 0.142+/-0.08, P=0.018). Children with E. histolytica-associated diarrheal illness were 2.93 times (95% CI 1.01-8.52, P=0.047) more likely to be malnourished and 4.69 times (95% CI 1.55-14.18, P=0.006) more prone to be stunted. Entamoeba histolytica-associated diarrheal illness was negatively associated with the growth of preschool children.