Adult rats of both sexes were given a single oral dose of [14C] patulin and were sacrificed at various time intervals from 4 hr to 7 days following administration of the mycotoxin. Two groups of rats were employed; the treated group had been exposed to daily oral doses of unlabeled patulin (dissolved in pH 5.0 citrate buffer) in utero and for 41-66 wk after weaning, while the controls were given the buffer only throughout gestation and for 38-81 wk after weaning. Approximately 49% of the administered 14C radioactivity was recovered from feces and 36% from urine within 7 days after dosing. Most of the excretion of labeled material occurred within the first 24 hr. All of the 14C activity detected in the urine samples was either metabolites and/or conjugates of the original [14C]patulin. About 1-2% of the total radioactivity was recovered as 14CO2 from expired air. Carbon-14 radioactivity in various tissues and organs was determined throughout the 7 day period; the most significant retention site was the red blood cells.