Studies in the male rat have shown that the dopamine D-2 receptor antagonists sulpiride and eticlopride, produce a dose-dependent prevention of the hypothermia induced by the D-1/D-2 receptor agonist apomorphine and the relatively selective D-2 agonist pergolide in the rat. In contrast, the D-1 antagonist SCH 23390 (given by the s.c. and i.p. route of administration) failed to prevent the hypothermic effect induced by both DA agonists, but tended to enhance the hypothermia caused by the two DA agonists. Thus, D-2 dopamine receptors appear to play a decisive role in the mediation of the hypothermic response of apomorphine and pergolide. There may also exist an interaction between D-1 and D-2 receptors in the expression of DA-agonist-induced hypothermia.