In this review we describe the application of markers which are useful for the diagnosis of soft tissue tumours in paraffin sections. Detection of intermediate filament proteins appears to be most useful for first screening of these neoplasms because all, except neuroblastomas, express vimentin; cytokeratin is expressed in synovial sarcomas, epithelioid sarcomas and mesotheliomas; desmin in myogenic tumours and glial fibrillary acidic protein in astrocytomas and gliomas. Tissue-specific markers are: factor VIII--related antigen-endothelial cells; myoglobulin and skeletal muscle myosin--skeletal muscle cells; neuron specific enolase--neurons and cells of the APUD systems; and leukocyte-associated antigen--leukocytes. Markers which are present in a variety of cell types and therefore do not serve as tissue-specific markers are; S-100 proteins, alpha-1-antichymotrypsin, creatine kinase M and actin. The S-100 antigens have been detected in melanomas, granular cell tumours, chondrosarcomas and in some schwannomas and liposarcomas. Alpha-1-antichymotrypsin has been found in fibrohistiocytic and 'true' histiocytic tumours and creatine kinase M and actin in myogenic tumours. No specific markers have, as yet, been described for fibrosarcomas, Ewing's sarcomas and hemangiopericytomas.