A new cell line (CCA) was established from a human embryonal rhabdomyosarcoma. It showed an "early" myogenic differentiation pattern: vimentin expression was found in 100% of cells, desmin in about 40% and myosin of the embryonic isoform in about 5%. Class I HLA expression on CCA cells was undeterctable but was greatly increased by in vitro treatment with human recombinant interferon-gamma and only marginally increased by human recombinant tumour necrosis factor-alfa. CCA cell line was tumorigenic in nude mice after either subcutaneous or intramuscular injection; macroscopic spontaneous metastases were not detected. The ability to induce metastatic nodules in the lungs was found when CCA cells were injected intravenously in cyclophosphamide-pretreated nude mice and, at low frequency, in untreated nude mice.