The kinetics of aluminum were determined in the rat. Intravenous bolus and oral doses of 8.1-mg/kg of aluminum as the chloride salt were administered to six rats. Serial blood samples and total urine and feces were collected and assayed for aluminum by atomic absorption spectrophotometry. The fraction absorbed orally (mean +/- SEM) was 0.27 +/- 0.03; the half-life was 5.29 +/- 0.47 h; the steady-state volume of distribution was 38.4 +/- 6.4 mL/kg, and the clearance was 8.87 +/- 1.76 mL X h-1 X kg-1. It was found that aluminum did not significantly penetrate the cellular components of blood. Plasma protein binding was determined to be approximately 98%. Sixty percent of the intravenous dose was excreted in the urine and the remaining 40% was excreted in the feces.