Objective: Malignant skin tumors rank amongst the most common forms of cancer worldwide and constitute a major challenge in dermatopathology and oncology research. This study aims to determine the frequency and patterns of malignant skin tumors at the University of Benin Teaching Hospital, Benin City, Nigeria. Methods: A 25-year (1982-2007) retrospective study of surgical day books and slides of all patients presenting with skin lesions was conducted at the Surgical and Pathology Departments of University of Benin Teaching Hospital. Results: A total of 694 skin biopsies were seen at the department during the study period; of these, 187 cases were malignant constituting 27% of all skin lesions. The majority of the malignant skin tumors (48%) occurred between the third and fifth decades with a male to female ratio of 1.4:1 and a mean age of 47 ± 29 years. Malignant melanoma was the most common skin malignancy, accounting for (n=61; 33%). Kaposi sarcoma constituted the second majority of the cases (n=56; 30%), with a markedly increased incidence between 2000 and 2008. This was consecutively followed by squamous cell carcinoma (n=45; 24%), basal cell carcinoma (n=18; 10%) and dermatofibrosarcoma protuberans (n=7; 4%). The leg and foot were the most common sites for malignant skin tumors. Conclusion: Malignant melanoma was the most common skin malignancy in this study. However, an increasing incidence of all malignant skin tumors was observed. This was particularly noticeable with Kaposi sarcoma, which may be attributed to the increasing prevalence of HIV/AIDS in Nigeria.