Introduction: Although the World Health Organization (WHO) has stated that cancer pain can be controlled in 85-97% of cases with knowledge and technology available today, effective pain control is about 40%. This situation emphasizes the necessity of discussing cancer pain again. Objective: This descriptive study was conducted with the aim of determining prevalence, severity, region and frequency of cancer pain in patients registered to a cancer treatment center. Materials and methods: A total of 256 patients who were treated in the outpatient clinic of a cancer center in Istanbul in 2010 constituted the study population and 99 cancer patients who agreed to participate in the study and could be reached constituted study sample. The study was completed with 49 (49.5%) patients as 50 (50.5%) out of 99 patients who were reached did not report pain. Results: Of the patients with cancer pain, 30.6% (n=15) had colon/rectum cancer, 24.5% (n=12) had lung cancer and 51% (n=25) had metastasis. Pain was in lower extremities in 34.3% (n=35), 57.1% (n=28) had moderate pain, 24.5% (n=12) had severe pain and pain was constant in 28.6% (n=19). Additionally, 20.4% (n=10) were not receiving pain treatment. Usually opioids, nonsteroidal anti-inflammatory drugs (NSAIDs) and adjuvant analgesics were being used in combination for pain treatment. Conclusion: The fact that 20.4% (n=10) of 49 patients were not receiving pain treatment and half of the cancer patients under control are experiencing pain is bothersome and thought provoking.