In this study we report on the variation in nuclear and cytoplasmic size of intermediate cells in normal cervical smears, in relationship to the week of the menstrual cycle and in relationship to the mode of contraception. A total of 18000 cells from 360 different women was studied. A significant difference in nuclear size of intermediate cells in smears from ovulating women not using contraception was found in comparison with intermediate cells in smears from women using contraceptive pills (ANOVA: F(1.312) = 4.98, p less than 0.02). Also a significant difference in the nuclear size of intermediate cells in smears from women using norgestrel- (or levonorgestrel)-containing formulas compared with lynestrenol-containing formulas was found (ANOVA: F(1.232) = 5.82, p less than 0.01). The influence of exogenous and endogenous hormones on cell populations in cervical smears is discussed. It is concluded that in studies on intermediate cells in cervical smears the contraceptive status of the women has to be taken into account.