Changes in the anterior pituitary in relation to the ovarian cycle and ovulation in female Scotophilus heathi are described. TSH, LH, FSH and PRL cells have been identified in the pars distalis (PD) by immunocytochemistry using the peroxidase-antiperoxidase technique. LH, FSH and PRL cells exhibited significant variation during the reproductive cycle of female S. heathi. The areal fractions of the PD occupied by LH and FSH cells were significantly (p < 0.05) higher during winter dormancy and the breeding phase as compared to the quiescence phase. The mean areal fraction of LH and FSH cells declined in March, following ovulation. The areal fraction of PD occupied by PRL cells varied from a minimum during winter dormancy to a maximum during pregnancy. Several of the PRL cells exhibited a degranulated appearance during winter dormancy suggesting PRL release. The areal fraction of TSH immunoreactive cells did not show a significant (p > 0.05) variation during the reproductive cycle. No evidence of involution was observed in the PD cells during the period of delayed ovulation.