Oxidative metabolism of [3H]diethylstilbestrol (DES) and the irreversible binding of reactive [3H]DES metabolites to the macromolecules in kidney slices of Syrian golden hamster were investigated. Non-extractable binding of [3H]DES to kidney macromolecules was observed after incubating hamster kidney slices under aerobic conditions (95% O2/5% CO2), but not under anaerobic conditions (100% nitrogen + 2 mM KCN). A number of oxidative metabolites of [3H]DES were detected in the incubation medium of kidney slices incubated under aerobic, but not anaerobic, conditions. The amount of radiolabeled macromolecules formed in male cortical slices under aerobic conditions increased with time of incubation. At a medium concentration of 50 nM [3H]DES, 0.08 pmole [3H]DES equiv./mg dry weight at 30 min and 0.19 pmole [3H]DES equiv./mg dry weight at 120 min were observed. The amount of irreversible [3H]DES-macromolecular complexes also increased with the concentration of [3H]DES in the incubation medium: 1.59 pmole [3H]DES equiv./mg dry weight was formed with 0.5 microM [3H]DES and 21.89 pmole [3H]DES equiv./mg dry weight was formed with 10 microM [3H]DES. Non-extractable [3H]DES binding was detected in all the subcellular fractions of hamster kidney with the highest amount in the microsomal and soluble fractions, followed by the mitochondrial and nuclear fractions. The macromolecular-[3H]DES complexes were solubilized by proteases but not nucleases, suggesting that [3H]DES irreversible binding is principally to the proteins and not the nucleic acids. The cortex as compared with the medulla of the male hamster kidney displayed a 5-fold greater capacity to irreversibly bind [3H]DES metabolites. The male hamster renal cortex showed a 2- to 3-fold greater capacity to form irreversible macromolecular-[3H]DES complexes than the female hamster renal cortex. These data demonstrate that: (1) renal oxidative metabolism of DES results in [3H]DES metabolites binding irreversibly to macromolecules; and (2) the sex and organ site specificity of the [3H]DES-macromolecular binding corresponds with the sex and organ site specificity of renal tumors of the hamster.