Interleukin-1beta (IL-1beta) and tumor necrosis factor (TNF alpha) induce prostanoid biosynthesis in vascular smooth muscle cells by promoting cyclooxygenase (COX) expression, but little is known about the biosynthesis of lipoxygenase (LPO) metabolites. We investigated the effects of human recombinant IL-1beta and TNF alpha on the production of arachidonic acid (AA) metabolites by high-performance liquid chromatography (HPLC). After being labelled with 3H-AA, cultured human pulmonary artery smooth muscle cells (HPASMC) were incubated with or without IL-1beta (200 U/ml) and TNF alpha (500 U/ml). The arachidonic acid metabolites released from HPASMC were then analysed by HPLC. In control HPASMC, 6-keto-PGF1alpha and PGE2 were the principal metabolites of the COX pathway, while 5-HETE, LTC4 and D4 were the main products of the LPO pathway. HPASMC treated with 200 U/ml of IL-1beta and 500 U/ml of TNF alpha produced more COX metabolites such as 6-keto-PGF1alpha, thromboxane B2, PGF2alpha and PGE2 than control cells. Significant increases in the production of LPO derivatives such as LTB4, C4, D4, and 15-HETE were also found in IL-1beta-treated HPASMC. Although the release of LPO products tended to increase in TNF alpha-treated cells, no significant change was noted. Many AA metabolites including LTB4 are responsible for the inflammatory process in vivo. AA metabolites produced by pulmonary artery smooth muscle cells might play important roles in cytokine-mediated acute lung injury and inflammation.