The effects of bromocryptine (CB-154) on prolactin (PRL) and luteinizing hormone (LH) secretion were studied in lactating sows and ovariectomized (OVX) gilts. In Exp]. 1, the litters of four sows were standardized to four pigs each at 20 to 30 d of lactation and a cannula was placed nonsurgically into the jugular vein of each sow. Twenty-four hours later (0800 h) blood samples were taken and two sows each were injected subcutaneously with 120 mg CB-154 or vehicle. Blood samples were then taken every 30 min for the next 23.5 h. An additional six sows whose litters were standardized to six pigs each at 28 to 30 d of lactation comprised EXp. 2. In Exp. 3, five puberal gilts were OVX. Forty-eight hours after OVX a cannula was placed into the jugular vein. The day after cannulation blood samples were drawn every 30 min from 0800 to 2400 h. Immediately after the sampling at 1200 h, two gilts were injected subcutaneously with 120 mg CB-154 and three were injected subcutaneously with vehicle. Exp. 4 was a repetition of Exp. 3 except that six gilts were OVX 10 d before the experiment and three each were treated with CB-154 of vehicle. Serum PRL concentrations were consistently depressed after CB-154 treatment in both the lactating sows (Exp. 1, from 35 to 5 ng/ml, and Exp. 2, from 45 to 7 ng/ml) and the OVX gilts (Exp. 3, from 20 to 13 ng/ml, and ?Exp. 4, from 9 to 2 ng/ml), but changes in serum LH concentrations after CB-154 treatment were not consistent among the four experimental groups. Therefore, we conclude that CB-154 depressed PRL secretion in the lactating sows and OVX gilts. In addition, CB-154 depressed LH secretion in the lactating sows, but the data are inconclusive as to whether or not BC-154 influenced LH secretion in the OVX gilts.