The effects of continuous intrarenal prostaglandin E2 (PGE2) infusion (7 days) on sodium and water balance, plasma renin activity (PRA), and sodium and water balance, plasma renin activity (PRA), and mean arterial pressure (MAP) were examined in conscious, unilaterally nephrectomized dogs maintained on a fixed sodium intake of 55 meq/day. PGE2 infusion (2 microgram/min) resulted in a sustained threefold increase in both urine output and water intake without a measurable change in glomerular filtration rate. PRA increased from 0.4 +/- 0.1 during the control period to 2.2 +/- 0.9 ng AI.ml-1.h-1 on day 1 and averaged 3.6 +/- 0.5 for the remaining 6 days of PGE2 infusion. Concurrently, MAP increased from 102 +/- 3 to a maximum of 117 +/- 4 mmHg on day 5; changes in PRA and MAP were significantly correlated (r = 0.96, P less than 0.001). Sodium excretion increased from 54.5 +/- 3 to 88.0 +/- 19 meq/day on day 1, and then declined to an average of 64.8 +/- 1 meq/day for the remaining 6 days of infusion. All variables returned to the control level during the recovery period. Intravenous infusion of PGE2 (2 microgram/min) yielded directionally similar but statistically insignificant effects. It is concluded that chronic intrarenal PGE2 infusion results in marked diuresis, polydipsia, a moderate loss of sodium, enhanced PRA, and mild hypertension.