We examined the rapid effect of resveratrol on nitric oxide (NO) production in endothelial F-2 cells. During an incubation period of 10 min, resveratrol at low concentrations (<20 μM) had no effect on NO production, whereas it significantly increased NO production at high concentrations (>50 μM). In contrast, pretreatment with resveratrol at low concentrations caused a significant decrease in vascular endothelial growth factor (VEGF)-stimulated NO production. Resveratrol failed to induce phosphorylation of endothelial NO synthase (eNOS) and VEGF receptor and did not affect autophosphorylation of the VEGF receptor. However, resveratrol markedly suppressed VEGF-induced eNOS phosphorylation. Resveratrol at high concentrations reduced the viability of F-2 cells as determined by 3-(4,5-dimethyl-2-thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and dye exclusion methods. Resveratrol-stimulated NO production was completely abolished by the depletion of extracellular Ca²⁺. These results indicate that resveratrol stimulates NO production by a Ca²⁺-dependent mechanism and reduces VEGF-stimulated NO production by impairing a Ca²⁺-independent mechanism in endothelial F-2 cells. However, the stimulatory effect of resveratrol may be partly attributed to its cytotoxicity.