The tissue distribution and excretion of an oral dose of 20 mg/kg of 14C-styrene was studied in both male and female rats at various time intervals after administration. Peak tissue levels were attained at or before 4 hours post administration. The organ with the highest concentration of radioactivity per unit weight was the kidney, followed, in order of decreasing concentration, by the liver and the pancreas. The data suggest a relationship between tissue distribution and kidney and liver toxicity. The high levels also found in the pancreas may bear some relationship to the reported increase in glucose tolerance in workers exposed to styrene. The principal route of excretion was via the kidneys, with 90% of the dose appearing in the urine within 24 hours of administration. Less than 2% of the dose was recovered from the feces.