Due to the development of more effective medications, those infected with HIV are living longer. Consequently, more tumors and infections have been added to the AIDS-defining criteria in the last decade. Our aim was to review the occurrence and clinical course of colorectal (CR) malignancies in HIV infected/AIDS patients from a single institution. A retrospective review of HIV/AIDS patients with colorectal malignant tumors was undertaken. We included adult patients, with ELISA and Western blot test positive for HIV, and primary malignant tumors located in the colon or rectum. Malignant neoplasms of the anus were excluded for the purposes of this study. Twelve patients (9 males and 3 females), mean age 41 years, were identified with the following neoplasm: 6 adenocarcinomas (ACA), 5 non-Hodgkin lymphomas (NHL), and 1 small-cell carcinoma. Intravenous drug abuse was the main risk factor for HIV. No patient had identified risk factors for colorectal neoplasm. Five out of six patients with ACA had metastatic disease at the time of diagnosis. One patient with stage II ACA developed early liver metastases after colonic resection. Seven out of 12 patients underwent surgery. Six (85.7%) of these sustained postoperative complications, primarily wound infection. The overall survival in our series was dismal, averaging 20 months. For NHL average survival was 29 months, and 12 months for CR-ACA. This is the largest series of cases of colorectal cancer in the HIV/AIDS patient population published in the English language and the largest number of colorectal ACA reported in this unique population. Early in our experience, tumors frequently found in immunoincompetent patients were detected (NHL). More recently, we have only treated patients with colorectal ACA; none of them had no risk factors for colorectal cancer (family history, IBD, FAP, HNPCC). These patients developed tumors at earlier ages and were diagnosed at an advanced stage. Therefore, these tumors may be associated with the grade of immunosuppression induced during the course of the HIV infection and with a tumorigenic effect of the HIV on the colonic epithelium. Consequently, a high index of suspicion when evaluating chronic abdominal complaints in such patients is warranted. The use of the new antiretroviral therapy regimens should be further evaluated to know its impact in the survival.