We have recently developed a thermal (infrared - IR) imaging system that allows accurate measurements of transient temperature distributions of the skin surface. It relies on active infrared imaging for the characterization of skin lesions. We hypothesize that lesions with increased proliferative potential or inflammatory processes in the skin generate quantifiable amounts of heat and possess an ability to reheat more quickly than the surrounding normal skin. We demonstrate that the visualization and measurement of the transient thermal response of the skin to a cooling excitation can aid the identification of skin lesions of different origin. In the preliminary studies we focused on optimizing this high-resolution infrared scanning system in order to evaluate thermal images of the skin with the aim to distinguish benign from malignant pigmented lesions. Such an imaging tool is expected to improve the diagnostic accuracy and sensitivity for melanoma as well as other skin cancers, while decreasing the number of unnecessary biopsies. Therefore, we are currently conducting a pilot clinical trial of our transient thermal imaging system to verify the feasibility of the described approach in distinguishing pigmented lesions of varying malignant potential. In our trial patients who possess a pigmented lesion with a clinical indication for biopsy are selected to participate in the study. After scanning the lesions, they are biopsied and graded for malignant potential. Biopsy results are correlated with thermal images and bright light images in order to evaluate thermal associations with malignant potential.