ABSTRACT: Pharmacokinetics and distribution of a 5 µg dietary dose of tributyltin (¹¹³Sn-TBT) and methylmercury (Me²⁰³Hg) were studied over 42 d in the American plaice Hippoglossoides platessoides, using in vivo gammacounting, whole-body autoradiography, and a 2-compartment model. The average retention efficiency of TBT was 42%, compared with 88% for MeHg. Both organometals were distributed to the entire body of the fish. Distribution proceeded at a faster rate forTBT, 95% of the steady state distribution being reached within 5 to 10 d, compared with 29 to 41 d for MeHg. Elimination of TBT was characterised by half-life values ranging from 15 to 77 d. Absorption of dietary TBT from the intestinal lumen appears tobe limited by its molecular size, whereas its fast translocation rate in the body of fish might be related to specific properties of the intestinal epithelium-blood interface or to co-transport with lipids. Our data also indicated that butyltins in theviscera were partitioned between 2 kinetically distinct pools; one that was eliminated rapidly and one that was stored or eliminated at a very slow rate, probably as a consequence of TBT metabolism. The overall biomagnification factor for the transfer ofTBT from sediments to benthic invertebrates to the American plaice may be >1. This indicates that the trophic transfer of sedimentary TBT in the marine benthic food web is potentially significant.