In a small-cell lung carcinoma (SCLC) tumor specimen as well as in 3 cell lines derived from SCLC biopsies obtained from the same patient at successive times during the clinical course, either the N-myc gene or the c-myc gene appeared to be amplified and expressed. The initial tumor specimen, a lymph-node metastasis, was amplified for N-myc, as was the cell line GLC-14 derived from this metastasis. The cell lines GLC-16 and GLC-19, derived from the recurrent primary tumor biopsies after a complete remission, were amplified for c-myc. This finding implies independent amplification events and supports the idea that the amplification of myc genes is probably a secondary event correlated with tumor progression. Although all 3 cell lines could be classified as classic SCLC cell lines according to their histological characteristics, GLC-16 and GLC-19 clearly possess, in their c-myc amplification and derivation from therapy-resistant tumor cells, features of variant SCLC lines. This may question the significance of the classic/variant classification.