Nine cell lines established from various malignant tissues of patients with small cell lung carcinoma (SCLC) were examined for chromosomal abnormalities and myc gene amplification. Cytogenetic studies revealed that all cell lines were aneuploid, often with a bimodal distribution with modal concentrations in the hypodiploid and hypertriploid range. With respect to chromosome #3, deletions of 3p were confined to six of nine SCLC "classic" lines. The region of overlap of the observed 3p deletions lies within 3p21-3p24 which is in agreement with previous assignments. Six of the nine lines tested with c-, N-, and L-myc probes showed an increase of between ten- and 100 fold in myc gene copy number. Coamplification of two or more of these genes was not observed in any cell line. Five of the six lines with myc gene amplification had cytogenetic markers of gene amplification either in the form of homogeneously staining regions (HSR) or double minutes (DM). Our results confirm that cytogenetically visible deletions of 3p are often present in cell lines established from patients with SCLC, and that mutually exclusive c-, L-, or N-myc gene amplification is also a common event in SCLC cell lines.