General practitioners (GPs) examine patients who attend a primary health care center. In the intervention group the computer-based clinical decision support tool "Nevus doctor" in a first step assists doctors in the process of selecting skin lesions that are suggestive of cancer. In the next step a given skin lesion is photographed using a dermatoscope attached to the lens of the camera. The dermatoscopic image is then processed by the computer program "Nevus doctor" and a preliminary result is presented. Finally the GP reviews the result and assesses the clinical significance of the output by using guidelines presented by "Nevus doctor". The patient is subsequently referred to a dermatologist and a complete skin examination is performed. The assessment of the dermatologist serves as the gold standard.