The pharmacokinetic disposition of intratracheally (i/t) and orally administered [3H]AFBt was studied in male Sprague-Dawley rats. Blood, urine and faeces were collected at selected intervals following administration of a single i/t or oral dose of AFB1 (600 μg/kg) in saline. Blood-concentration data from both groups approximated a two-compartment open model. The time-to-peak for the i/t group (hr) was less than that for the oral group (3 hr), but the disappearance of label from the blood followed a nearly identical course in both groups. The plasma half-lives (Image ) were 87.7 and 91.8 hr for the i/t and oral groups, respectively. In addition, urinary and faecal excretion profiles were similar. By day 23, urinary excretion of label had accounted for 16.4 and 15.0% of the dose in the i/t and oral groups, respectively, and faecal excretion for 56.0 and 54.6%. At this time, however, significantly more label was recovered from the lungs and upper airways of the rats of the i/t group than in those treated orally.