The effects of systemic intravenous (i.v.) infusion of adenosine on renal blood flow and glomerular filtration in eight healthy, awake females have been examined. Renal blood flow and glomerular filtration rate were measured as the clearance of para-aminohippuric acid (PAH) and inulin, respectively. Following basal sampling adenosine was infused i.v. at successive rates of 60 and 80 micrograms kg-1 min-1 for 30 min at each rate. Plasma clearance of PAH showed a minor, but non-significant, increase from 697 +/- 41 to 775 +/- 97 ml min-1. However, the arterial plasma concentration of PAH decreased by 17 +/- 4% (P < 0.001), indicating that there was a small increase in renal blood flow. Inulin clearance was reduced from 123 +/- 14 to 88 +/- 11 ml min-1 1.73 m-2 (P < 0.01). The resulting filtration fraction was reduced from 18 +/- 1 to 11 +/- 1 (P < 0.001). The K+/Na+ excretion ratio increased from a basal value of 10 +/- 1 to 42 +/- 11 (P < 0.01) at the highest dose of adenosine, and renal oxygen consumption decreased from 17 +/- 2 to 9 +/- 1 ml min-1 (P < 0.001). In conclusion, i.v. infusion of adenosine in healthy, awake subjects causes a minor increase in total renal blood flow and a marked reduction in glomerular filtration. This shows that adenosine also exerts a vasodilatory effect in the renal circulation, primarily on postglomerular arterioles. In addition, adenosine may produce an aldosterone-like effect on salt excretion, and a reduction in renal oxygen consumption.