In vivo cutaneous surface microscopy, epiluminescence microscopy, dermoscopy, dermatoscopy and magnified oil immersion diascopy, are terms that describe the use of an incident light magnification system to examine cutaneous lesions, usually with immersion oil at the skin-microscope interface. The result is the visualization of a multitude of morphological features, not visible with the naked eye, that enhance the clinical diagnosis of nearly all pigmented lesions. Sixty-two invasive melanomas and 159 randomly selected non-melanoma pigmented lesions were used in the study. The non-melanomas, while randomly selected from a large data base, were all clinically atypical. Using the x 10 magnification of hand-held surface microscopes (Dermatoscope, Episcope), we present an analysis of 72 surface microscopic variables (constituting over 15,000 single observations) for the diagnosis of invasive melanoma. Forty of the 72 features studied were shown to differ significantly between invasive melanoma and non-melanoma pigmented lesions. Blue-white veil, multiple brown dots, radial streaming and pseudopods had a specificity greater than 95% for melanoma. Two features, symmetrically irregular pigment (non-uniform pigmentation with point and axial symmetry) and the presence of a single colour, had a sensitivity of 0%, i.e. were absent, in melanoma. The other significant features are presented, with their sensitivity and specificity for melanoma.