The aim of the study was to estimate the prevalence and localization of different tumors in the urogenital system in dogs and cats in relation to sex, age and breed of animals. The study was performed on tumors or tissue specimens from tumors of the urinary and genital system obtained during surgery from dogs and cats submitted to the Division of Pathological Anatomy, Department of Clinical Sciences Agricultural University of Warsaw from 1998 to 2005. Most tumors of the urogenital system recognized in the present study derived from dogs (94.20%, 130 cases), and only a few cases were obtained from cats (5.79%). Occurrence and localization of urogenital system tumors in present review is similar to findings reported by other authors. Testicular tumors in males, ovarian lesions in females and urinary bladder tumors in both sexes were most commonly recognized. Older dogs were most often affected, animals with nonmalignant tumors were a bit younger than those with malignant lesions. Any obvious breed predilections were found, but terriers were at increased risk for development of transitional cell carcinoma of the urinary bladder and mixed breed and German shepherd for development of testicular neoplasms.