This study examined the morphology, in vitro growth, and two genetic responses to serum stimulation in the nonsmall cell lung cancer (NSCLC) cell lines SK-Lu-1, SK-MES-1, A427, and A549. Morphologically, all four were NSCLC: SK-Lu-1 was undifferentiated, the remainder were adenocarcinoma variants. SK-Lu-1 and SK-MES-1 were slow growing with low-anchorage independent growth capacity; the A427 and A549 lines were fast growing with high-anchorage independent growth capacity. All of the lines expressed basic fibroblast growth factor (bFGF) as a dominant 7.1 kb transcript at amounts significantly lower than in control human lung fibroblasts. bFGF expression could be upregulated by serum exposure in several nontransformed human cell lines, but only the SK-Lu-1 NSCLC cells increased bFGF after serum exposure (482%) compared with a peak increase of 1222% in the fibroblast controls. All of the NSCLC cell lines increased c-fos in response to the same serum stimulations. These results show that growth-factor gene expression can be modulated in NSCLC, and that significant differences exist among NSCLC cell lines commonly used as laboratory correlates of human disease.