A comparative analysis was performed on the electrophysiological properties of 11 neoplastic neurogenic cell culture lines and 5 other cell lines of different origin (HV1C, rat bile duct carcinoma; BICR/M1RK, rat mammary tumor; HeLa, human cervix carcinoma; 3T3, mouse embryo [fibroblasts]; REe, rat embryo). Neurogenic lines were derived from N-ethyl-N-nitrosourea-induced neoplasms of the nervous system or cultured fetal rat brain cells that underwent neoplastic transformation in vitro after exposure to N-ethyl-N-nitrosourea in vivo. Electrical membrane excitability was lacking in all neurogenic cells analyzed. Their membrane potential and input resistance values were similar to those of the nonneurogenic lines. Intercellular ionic coupling was consistently observed between cells of a fibroblastoid shape or cells bearing multiple cytoplasmic processes (i.e., all neurogenic lines HV1C, BICR/M1RK and 3T3). Epitheloid cells (i.e., HeLa, REe and NV1C [neurinama] subpopulation and a GV1C1 [glioma] variant) showed no such intercellular communication. In vivo monolayer cultures on glass coverslips were obtained by a modified i.p. diffusion chamber technique. Under those conditions, the cells (with the exception of a glioma-derived cell line) retained the morphological appearance and electrophysiological properties observed in vitro.