Clinical guidelines for the diagnosis of pigmented skin lesions are not always reliable. Incident light microscopy provides an interesting approach to solving this problem. For this investigation a stereomicroscope, a glass slide and immersion oil are used. The various in vivo criteria of this method, which go beyond the changes discernible by the naked eye, are correlated with the histopathological structures. Incident light microscopy opens up a new dimension of clinical morphology for the diagnosis and differential diagnosis of malignant melanoma, dysplastic nevi or non-melanocytic pigmented neoplasms and facilitates a more precise preoperative assessment of these lesions.