Resistance of hormone-dependent mammary carcinoma to cisplatin as a potent antitumor agent led to the synthesis of other estrophilic platinum complexes. In this investigation, the effects of a newly synthesized estrogen-receptor affine platinum complex on the mouse uterus were studied using light and electron-microscopy. The results have been compared with Tamoxifen, cisplatin and the estrophilic ligand. Both estrophilic ligand and estrophilic platinum complex produced strong estrogenic effects as well as features characteristic of the uterine epithelial cell in the luteal phase of the cycle, corresponding to a massive stimulation of the surface and glandular epithelial cells. The uteri showed large glandular lumina. An increase in the number of multivesicular and residual bodies, accompanied by a proliferation of eosinophilic granulocytes, was also seen. The appearance of inter- and intracellular lumina and the activation of smooth muscle cells represent further characteristic effects of the estrophilic ligand and estrophilic platinum complex. Anticipated increases in the incidence of cell death and/or deviant cyto-nuclear architecture in the uteri treated with cisplatin or platinum complex, were not observed.