There is a lack of systematic nephrographic studies on epidemic nephritis (EN). We studied 10 patients with EN using [99Tcm]MAG3 gamma camera nephrography and followed up 9 of them 22-68 days later when they had clinically recovered. Variables for renal clearance of [99Tcm]MAG3 and the retention of radioactivity in the kidneys and blood were calculated. In all patients renal function was impaired acutely. There was marked reconstitution of renal function in the control studies. [99Tcm]MAG3 clearance was inversely related to serum creatinine. On visual inspection the nephrograms showed no focal changes. Nephrography was more sensitive than sonography at identifying renal impairment. [99Tcm]MAG3 nephrography is a sensitive method for identifying renal involvement and reconstitution of renal function in EN. It may be a valuable adjunct to the diagnostic arsenal, especially in nonendemic areas where EN occurs only sporadically and where there may be diagnostic uncertainty in patients presenting acutely with EN.