In this study, vaginal smears taken from 400 patients were examined cytologically using the Papanicolaou technique. Twenty of the 400 patients were detected as harbouring Trichomonas vaginalis. The interactions of T. vaginalis with epithelial cells, polymorphonuclear leucocytes (PMNLs) and erythrocytes were determined at light microscopic level. It was observed that T. vaginalis were juxtaposed to the epithelial cells and changed shape according to the contours of the epithelial cell revealing the cytopathic effect of trichomonads on epithelial cells. Trichomonads attached to PMNLs produced pseudopodia to phagocytose the cells. Occasionally an amoeboid shaped T. vaginalis organism was seen trailed by a row of PMNLs. This light microscopic study supports the production by trichomonads of a chemotactic factor for PMNLs. Phagocytosed erythrocytes were also seen in the cytoplasm of T. vaginalis, suggesting the need for the patient to be tested for anaemia.