The neural crest gives rise to a variety of tissues, including peripheral neurons, Schwann cells, melanocytes and ectomesenchymal cells, which include the smooth-muscle cells of large arteries. Cell lines derived from neuroblastoma (a neural-crest tumor) exhibit at least 2 distinct morphological cell types, a neuroblastic phenotype (N-type) and an epithelial-like phenotype (S-type) with characteristics of substrate-adhesiveness. We have analyzed 17 human neuroblastoma cell lines using a panel of monoclonal antibodies (MAbs) against cytoskeletal proteins. Three neuroblastoma cell lines (KP-N-SI, KP-N-YN and SMS-KCN) bound an alpha-smooth-muscle actin antibody. In addition, one of these lines (KP-N-SI) bound anti-desmin MAbs as determined by indirect immunofluorescence. A total of 8 cloned cell lines were obtained from the above parent cell lines. These were composed of either N- or S-type cells and were confirmed to have the same neuroblastoma origin as each parent cell line by chromosomal analysis. Alpha-smooth-muscle actin and desmin were demonstrated in the S-type cloned cells by indirect immunofluorescence, as well as by 2-dimensional Western blot analysis. These results were confirmed by Northern blot analysis using a specific probe (pSH alpha SMA-3' UT) to human alpha-smooth-muscle actin mRNA. These ascertain the presence of alpha-smooth-muscle actin and desmin in neuroblastoma cell lines. These data show that, in addition to giving rise to cells with neural, Schwann-cell and melanocyte markers, neuroblastoma can also give rise to the cells expressing smooth-muscle cell markers.