The human vagina is known to be heavily innervated by vasoactive intestinal polypeptide (VIP) immunoreactive nerve fibres. In the present study we have examined the effect of VIP (900 pmol x kg-1 x h-1, IV during 30 min) on vaginal lubrication and blood flow in fourteen normal non-pregnant women. Vaginal blood flow was measured by the heat clearance technique and the vaginal lubrication quantified by the weight gain of preweighed filter papers placed on the surface of the vaginal wall for 30 min. Arterial blood pressure, pulse frequency and the concentration of VIP in peripheral blood were monitored. VIP (median concentrations of 200-300 pmol x l-1) induced a significant increase in vaginal blood flow accompanied by a 100% increase in vaginal lubrication (from 27 mg/cm2 to 53 mg/cm2). The VIP infusion lead to a significant increase in pulse frequency and a significant fall in diastolic arterial blood pressure. The findings suggest that VIP may participate in the control of the local physiological changes observed during sexual arousal: genital vasodilation and increase in vaginal lubrication.