During a designated period(Jan. 2003$sim$Jun. 2006), a total of 2,051 biopsy and necropsy cases submitted to Veterinary Medical Teaching Hospital of Seoul National University and local practitioners were diagnosed as canine tumors based on microscopic evaluation in the Department of Veterinary Pathology, College of Veterinary Medicine, Seoul National University. Four hundred and twenty of 2,051 tumor specimens excluding mammary(883, 43.1%) and cutaneous(748, 36.5%) tumors were included in this retrospective study. They were composed of genital tumors(189, 45.0%) followed by alimentary(113, 26.9%), hematopoietic(52, 12.4%), urinary(20, 4.8%), bone & joint(15, 3.6%), ocular & otic(9, 2.1%), respiratory(6, 1.4%), endocrine(6, 1.4%), and miscellaneous(10, 2.4%). Particular top ten tumor most frequently diagnosed were seminoma(48, 11.4%) followed by fibrous epulis(38, 9.0%), lymphoma(38, 9.0%), leiomyoma(33, 7.9%), fibroma(26, 6.2%), ovarian cyst(19, 4.5%), melanoma(15, 3.6%), papilloma(14, 3.3%), cystic endometrial hyperplasia(13, 3.1%), granulosa cell tumor(13, 3.1%) in descending order comprising 257(61.2%). The affected age of the animals with ten frequent tumors ranged from 3 months to 17 years old with a mean of 9.2 years old(n=218). There were no significant sex prevalence except female leiomyoma. The top seven anatomical sites of tumors inclusive were gingiva(62, 14.8%), testis(61, 14.5%), ovary(48, 11.4%), vagina(40, 9.5%), uterus(36, 8.6%), lymph node(30, 7.1%), and spleen(21, 5.0%).