The effects of handling and ether stress on serum prolactin (PRL) levels in gonadally active and gonadally regressed male golden hamsters and in females in different stages of the estrous cycle were examined. Males, regardless of reproductive state or photoperiod, showed no significant alterations in serum PRL levels following exposure to ether and cardiac puncture, in contrast to females, which showed a significant elevation in serum PRL following these two procedures. This increase was small and inconsistent in females etherized for 1 min, but it was very pronounced in females etherized for 6 min. In females there was also a slight but significant increase in PRL following transfer from the animal room to the laboratory. Thus, routine experimental manipulations, such as moving the animals to a laboratory and ether exposure, induce significant and variable elevations of serum prolactin in female hamsters.