Furosemide, a potent loop diuretic, has been reported to cause xerostomia, a sensation of oral dryness. We obtained urine and salivary secretions from five normal males after oral intake of either 0.5 mg/kg body weight of furosemide or placebo. The experimental treatment resulted in a five-fold increase in urinary output. In contrast, analysis of salivary secretions indicated there were no significant differences in flow rates, total output, total protein, or Na+, K+, or Cl- concentrations following drug or placebo. Subjectively, xerostomia was experienced 10 times more frequently after ingestion of furosemide. These data suggest that, in vivo, furosemide had a greater effect on the kidney than on the salivary gland and that the sensation of oral dryness is not solely a function of the quantitative salivary output.