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Background: Clinical guidelines for the diagnosis of pigmented lesions of the skin are not always reliable. Especially the differential diagnosis between benign dysplastic nevi (Clark's nevi) and early melanomas, as well as between melanocytic and nonmelanocytic skin tumors (seborrheic keratoses, pigmented basal cell carcinomas and angiokeratomas) is often difficult., Objective: Surface microscopy, which is performed today under various synonyms (dermoscopy, dermatoscopy, epiluminescence microscopy, incident light microscopy, skin microscopy), has been shown to provide additional features and subtle clues for the assessment of pigmented skin lesions., Methods: The pigmented lesions are covered in vivo with a drop of immersion oil and a glass slide, and observed in incident light by using a stereomicroscope (magnification 6- to 40-fold) or a hand-held instrument called dermatoscope (magnification 10-fold). The immersion oil renders the stratum corneum translucent and allows a better observation of distinctive alterations of the dermoepidermal junction and the papillary dermis., Results: The various criteria of surface microscopy (e.g. pigment network, black dots or irregular extensions) that cannot be discerned by the naked eye are summarized and discussed in detail. The diagnostic significance but also the limitations of this technique are emphasized., Conclusion: Surface microscopy opens up a new dimension of clinical morphology for the diagnosis of pigmented skin tumors and facilitates a more reliable assessment of the lesions.