The effects of intravenously administered prostaglandin D2 (PGD2) on bronchopulmonary and cardiovascular functions were examined in the dog. PGD2 (0.03-1.0 microng/kg) was shown to be more active than PGF2alpha, a known bronchoconstrictor, in decreasing dynamic lung compliance, tidal volume, and expiratory airflow rate, as well as in elevating lung resistance. PGD2 demonstrated a potency approximately 4-6 times that of PGF2alpha on pulmonary mechanics. Atropine sulfate infusions reduced significantly the resistance and compliance responses to PGF2alpha, but only the resistance responses to PGD2, thereby suggesting that part of the bronchoconstrictor activities of these agents involved a cholinergic component. In another series of anesthetized dogs, PGD2 (0.1-10.0 microng/kg) increased pulmonary arterial pressure (comparable to PGF2alpha) and heart rate (greater than PGF2alpha, but less than PGE2), while concomitantly decreasing systemic arterial pressure in a dose-related manner (1/10 that of PGE2). Qualitatively similar alterations in cardiovascular parameters were obtained for PGD2 in conscious dogs. Therefore, potent biologic activity of PGD2 has been shown in the dog. No physiologic or pathologic role for PGD2 has yet been demonstrated, but nonetheless, since it is a naturally occurring PG derived from arachidonic acid, further studies are warranted.