In the present investigation, interleukin 6 (IL-6) activity in the supernatant of cultured mouse peritoneal macrophages was monitored using a sensitive bioassay involving the IL-6-dependent murine hybridoma B9 cell line. The effects of resveratrol on Il-6 release by mouse peritoneal macrophages stimulated with calcium ionophore A23187 and fMLP were explored. Resveratrol, at a concentration range from 5 x 10(-6) to 4 x 10(-5) mol.l-1, was found to dose-dependently inhibit IL-6 release by cultured macrophages induced by A23187 and fMLP, and showed no direct cytotoxic effect, but induced proliferation of cultured mouse thymus cells. Resveratrol, at a concentration range from 10(-8) to 10(-5) mol.l-1, was shown to dose-dependently inhibit calcium ion influx into the cells with the stimulation of fMLP (10(-6) mol.l-1). These results suggest that the blocking of calcium ion influx into cells by reveratrol is one of the possible mechanisms of the IL-6 biosynthesis inhibitory action of resveratrol.