Causes of pain were analysed in 200 patients referred to a specialized cancer pain clinic. Pain caused by tumour growth was found in 158 patients, pain secondary to cancer or its treatment in 116 patients and pain unrelated to cancer in 33 patients. Visceral involvement (74 cases), bone metastases (68 cases), soft tissue invasion (56 cases) and nerve/plexus pressure or infiltration (39 cases) were the most frequent causes of pain due to tumour growth. Myogenic pain (68 cases) was the most frequent cause of secondary pain. The patients presented with a multitude of different combinations of causes of pain, the majority having at least two separate causes. Since pain treatment in cancer patients should be determined by its aetiology, a detailed analysis of the pain condition in each patient should form the basis for a rational therapy.