A 4 and 8 month old boys and 1,5 year boy presented with a 6 week history of a skull mass of the anterior fontanelle. The mass was excised, and the histopathologic features were diagnostic for melanotic neuroectodermal tumor of infancy. The tumors consisted of a biphasic cell population in a fibrous stroma. The small, darkly staining cells comprising the first population stained positively for NSE, chromogranin and synaptophysin, showing them to be neuroblasts, and the large epithelioid cells comprising the second cell population stained positively with the antibodies CK7, HMB 45, Melan A and TTF 1, showing them to be melanocytes. Ultrastructural examination confirmed the biphasic nature of the tumor cells, with secretory granules and neurofilaments in the neuroblastic population, and melanosomes in the epithelioid population. It is the identification of the epithelioid cells in the smears which differentiates this tumor from other round cell tumors of infancy and helps in the correct diagnosis. These results add to the evidence supporting the neural crest origin of melanotic neuroectodermal tumor of infancy and confirm its formation from two distinct cell lines.