Vitellogenesis was monitored in Clarias gariepinus females during puberty and after artificially induced ovarian recrudescence. In two experiments (with pubertal and adult females, respectively), the effect of male stimulation of vitellogenesis was assessed by weekly sampling of females kept with males of exposed to male+female holding water. The parameters examined were the gonadosomatic index (GSI), the proportion and diameter of exogenous vitellogenic oocytes, and plasma levels of estradiol (E 2) and vitellogenin (VTG). In pubertal females the pattern and sequence of appearance of these parameters are in general agreement with data from other teleosts: a peak in E 2 values precedes a peak in VTG, resulting in an increase of GSI and in a concomitant change in yolk deposition in the oocytes. Stimulation causes both a shift in timing and an increase in levels of plasma E 2 and VTG, resulting in faster ovarian growth. In adult females, stimulation of vitellogenesis, although resulting in distinct differences in GSI and ovarian development, is not accompanied by a shift in timing of plasma E 2 and VTG. E 2 values tend to be higher in stimulated adult females. These differences between first and subsequent cycles are thought to be due to the extremely short recrudescence period of C. gariepinus in captivity.