The acute biochemical effects of the nephrotoxin p-aminophenol (PAP) were studied in detail using a combination of conventional bioanalytical and 1H-NMR spectroscopic methods. Dosing PAP (25-100 mg/kg) to male F344 rats resulted in a dose-related proximal nephropathy with consequent elevations in urinary enzymes, glucose, and urine total protein as shown by conventional methodology. 1H-NMR spectroscopy at 400 MHz of urine from PAP-treated rats also revealed a characteristic glycosuria, with concomitant amino aciduria. The increased excretion of these compounds indicates functional defects in the proximal tubule and reduced solute reabsorption efficiency. In addition, 1H-NMR urinalysis and conventional enzymatic analysis showed a dose-related lactic aciduria. Other changes detected by 1H-NMR included a dose-related reduction in the excretion of citrate (confirmed by a conventional biochemical method) and an increase in the excretion of acetate. The degree of abnormalities shown by 1H-NMR urinalysis agreed well with histopathological observations and conventional biochemical indices of nephrotoxicity. 1H-NMR urinalysis therefore serves to highlight changes in the excretion of low MW urine components not routinely studied by conventional biochemical analysis.