Using infrared thermography, 264 in patients who were clinically suspected of having primary malignant melanoma (mM) of the skin were examined with regard to the thermographic pattern of both tumor and peritumoral skin area. In 84% of the patients with histologically confirmed mM deviations from normothermic pattern (mainly hyperthermic) were found of the tumor itself and/or the peritumoral area. All nodular mM proved to be hyperthermic. Pigmented skin tumors other than mM (e.g., angioma, basalioma, nevus cells, mole, histiocytoma) predominantly exhibited local isothermia or only minor thermographic changes. The infrared radiation intensity of the mM depended on the individual surface attributes of the tumors. As a rule, the larger mM are warmer than small mM. When comparing histological staging of a mM with thermographic classification, the pT values were strongly correlated with the thermographic values, ranging from Q1 to Q4. The highest measurements of infrared radiation were obtained in the nodular and acrolentiginous mM, as compared to the other melanoma types. There is evidence that mM exhibiting marked local hyperthermia have a particularly to poor prognosis.