Fenretinide has been used orally as a chemopreventive retinoid in a trial for women at risk of developing contralateral breast cancer. The levels of fenretinide and its metabolites were measured in the breast tissue obtained at surgery from women in the trial. Fenretinide was concentrated by breast tissue. Two major metabolites were detected in the tissue extract, one co-eluting with N-(4-methoxyphenyl)retinamide (4-MPR), and the other, more polar, eluting at 17 min under the conditions used. This metabolite remains unidentified. Division of the breast tissue into epithelial cells and fat fractions revealed that fenretinide and the metabolite at the 17 min peak were concentrated in the epithelial cells, whereas 4-MPR was principally localised in the fat compartment. Thus fat may serve as a storage compartment for the retinoid.