Embryonal rhabdomyosarcoma is the most frequent of tissue sarcomas in children. Its location in the subcutaneous tissue makes it a dermatological diagnosis. In childhood, the exact histological type of the tumour, sometimes difficult to determine, is absolutely necessary since prognosis and treatment differ according to the histogenetic form. Rhabdomyosarcoma is rare in adults. One must rule out malignant pleomorphic histiocytoma which has a more favourable prognosis. Among the antisera recently made available, those directed against desmin, foetal skeletal myosin and/or specific skeletal muscle myofilament seem to be most useful when associated with the anti-myoglobin antibody.