The purpose of this research was to investigate effect of dietary betaine on intestinal morphology after an experimental coccidiosis. Hence a total of 189 male and female broiler chicks were randomly assigned to 9 floor cages. Chicks were fed a basal diet supplemented with 0, 0.6 or 1.2 g kg(-1) betaine. All birds were inoculated orally with Eimeria oocysts on day 28. Duodenal morphology parameters and lesions were scored by microscopic observation on intestine samples which were taken at day 42 of age. Adding 1.2 g kg(-1) betaine to diet diminished intestinal lesions (p < 0.05). Dietary supplementation with 0.6 or 1.2 g kg(-1) betaine significantly (p < 0.01) increased intraepithelial lymphocytes as well. Level of additive betaine had no effect on the ratio of villus height/crypt depth or villus surface area. Lamina propria of duodenum became thicker in the intestine of chickens which received more supplemental betaine via their diet. In conclusion, since the number of intraepithelial lymphocytes and thickness of lamina propria represent the condition of gut immune response, it seems that dietary betaine may immunomodulate the gastrointestinal tract of broilers. In addition, betaine effect on villus morphology measured later in life differed from what had been measured already earlier in life of the chicks.