The status of the neural cell adhesion molecule NCAM gene which is mapped to human chromosome 11q23-24 has been investigated in Ewing-tumor-derived cell lines which present the t(11;22)(q23-24;q12) translocation characteristic of this malignancy. No rearrangement was detected when 2 different non-overlapping probes to mouse NCAM were used. The expression of the NCAM gene was analysed at both the protein and messenger levels in material extracted from Ewing cell lines, human neuroblastoma cell line and fetal mouse brain. Immune blot and immunoprecipitation studies showed that the neuroblastoma cell line contained more NCAM material than the Ewing lines. In neuroblastoma but not in Ewing, the NCAM material had the electrophoretic characteristics of molecules with long polysialic acid chains. After treatment with endosialidase, the diffusely migrating neuroblastoma material was resolved into 3 discrete bands of 120, 140 and 180 kDa. In Ewing extract, high-molecular-weight NCAM species were also detected with a 3-band pattern more reminiscent of mature brain. Endoglycosidase F treatment of Ewing NCAM indicated that all 3 species were largely N-glycosylated. Northern blot analysis confirmed that NCAM was expressed more abundantly in neuroblastoma than in Ewing cell lines. Among the 4 NCAM messengers (7.0, 6.5, 4.3 and 4.1 kb) detected in the neuroblastoma, the 6.5 kb species was largely predominant. The Ewing messenger RNA pattern was clearly different as the largest 7.0-kb species was virtually absent and the other bands were of similar intensities.