The aim of the study was to screen the malignancy in an acromegalic patient group and to determine whether there was any increased risk and the incidence of malignancy and its association with disease characteristics such as duration of disease, latency in diagnosis, and GH and IGF-1 levels. One hundred-five (65 female, 40 male) patients with acromegaly followed and treated at Cerrahpasa Medical School, Endocrinology and Metabolism outpatient clinic between 1983 and 2007 were included in this study. The patients were screened with colonoscopy, mammography, and thyroid and prostate ultrasonography (US). Malignancy was detected in 16 (15%) patients. Thyroid cancer was found in 5 patients (4.7%), breast cancer in 3 (2.8%), colon cancer in 2 (1.9%), lung cancer in 2 (1.9%), cervix cancer in 1 (0.9%), myelodysplastic syndrome (MDS) in 1 (0.9%), cholangiocarcinoma in 1 (0.9%), and multiple endocrine neoplasm (MEN) type 1 in 1 patient (0.9%). Cancer was more common in the male patients (P = 0.046) and high levels of GH increased the risk of cancer development (P = 0.046). In this series, the most commonly detected cancer types were thyroid followed by breast and colon cancers. Although high levels of initial GH seemed to increase the risk of cancer development in acromegalic patients, age, gender, age at the time of diagnosis, duration of disease, and initial IGF-I levels were not associated with cancer development.