Steadily declining numbers of breeding sheep accentuate the need for critically examining and improving production practices to maintain lamb production and preserve marketing and processing facilities. Alterations of breeding management to incorporate exogenous hormonal compounds is one possible means of increasing lamb production per ewe. Sheep usually mate when periods of light are less than 14 hours. The normal breeding season at this latitude begins in early August and lasts until mid-January. During this period daylight length and possibly temperature play a role in initiating changes in hormonal secretion which in tum regulates estrual activity. Improved seasonal breeding by synchronization of estrus in the ewe flock and more repeatable out-of-season breeding are desirable to increase year around lamb production and reduce seasonal fluctuations in cost. Synchronization or stimulating ewes to exhibit estrus and conceive could result in: 1) earlier lambing dates, 2) a shorter lambing season, 3) reduced labor requirements during lambing, and 4) a more uniform lamb crop. Out-of-season breeding, as the term implies, is breeding ewes out of the normal breeding season to produce fall lambs. This practice could be utilized to increase total lamb production. By stimulating ewes with exogenous hormones in the spring of the year, out-of-season breeding can occur and a potential fall lamb crop produced. The series of experiments reported herein were conducted to evaluate the effects of various exogenous hormonal compounds on the regulation of estrual activity in both cycling and noncycling (anestrous) ewes.