AIM To investigate the effect of erythromycin on nitric oxide(NO) pathway and calcium ion in culture human umbilical vein cells. METHODS The level of NO and nitric oxide synthase (NOS) activity were measured by NO and NOS kits. The intracellular free calcium concentrations were measured with Fura-2/AM. RESULTS Erythromycin significantly increased NO production and intracellular free calcium concentrations in HUVEC. It could also markedly increase NOS activity in a dose and time dependent manner. CONCLUSION The possible mechanism of this effect is attributed to the change of intracellular free calcium.