Three neuroblastoma cell lines established from tumor samples obtained from one patient are described. The three lines were derived from bone marrow aspirates taken at diagnosis, and 13 and 15 months later. The origin of the cell lines PER-106, PER-107, and PER-108 from malignant neuroblasts was confirmed by electron microscopy studies, surface marker analysis, and assessment of MYCN amplification. Cell lines PER-107 and PER-108, which were established from tumor samples obtained at the time of progressive disease, have significantly shorter doubling times than PER-106 and grow mainly substrate-adherent, while cell line PER-106 (established from sample obtained at diagnosis) consists of small round neuroblastic cells which form large aggregates in suspension culture. The electron microscopy studies revealed distinctive neuroblast-like ultrastructure in all cell lines. The MYCN copy number was amplified (> 10 copies) in the established cell lines and in the fresh tumor samples and the relative abundance of MYCN RNA in the cell lines correlated roughly with the extent of the MYCN gene amplification. However, distinct phenotypic differences can be demonstrated among these three lines, which provide a model for the further examination of this highly malignant tumor. Detection of MYCN amplification by chromosomal in situ hybridization was performed on this set of cell lines, as reported by McRobert et al. (this issue, pages 128-134).