Abstract
Sacrifice of 69 fat sand rats (Psammomys obesus) bred at the Hebrew University-Hadassah Medical School, yielded 19 cases with spontaneous uterine tumours. These consisted of 5 leiomyomas, 3 endometrial polyps, 10 adenofibromas and one possibly malignant mixed mesodermal tumour. The relatively high incidence of adenofibromas histologically resembling the human neoplasm, could make this animal a useful model for further study of Müllerian mixed tumours.