A new permanent cell line (GRU-1) derived from the lymph-node metastasis of a human epithelioid sarcoma was established in tissue culture. Immunohistochemically, the original tumor had exhibited an intriguing potential for multidirectional differentiation with features of mesenchymal, epithelial and neural differentiation, evidenced by the co-expression of vimentin, cytokeratins and neurofilament proteins, respectively. This capability for multidirectional differentiation was fully preserved in the cultured cells. GRU-1 tumor cells proved to be uniformly positive for vimentin and a considerable proportion of the tumor cells exhibited a positive reaction for cytokeratins and neurofilament proteins. The neural markers neuron-specific enolase (NSE) and synaptophysin were observed in a small proportion of GRU-1 cells. Ultrastructurally, GRU-1 cells showed desmoplastic activity in vitro, being enmeshed by collagen fibrils. DNA distribution, as studied by flow cytophotometry, revealed DNA-diploidy (DNA index = 1) and a G0/G1-proportion of 70.5%. After heterotransplantation in nude mice, GRU-1 tumor cells expressed vimentin and cytokeratin only, whereas the neural markers could not be further demonstrated.