Neuroendocrine hamster lung tumors, induced by exposure to 60% hyperoxia and subcutaneous administration of the tobacco-specific nitrosamine 4-(methylnitrosamino)-l-(3-pyridyl)-l-butanone (NNK) for 12 weeks, were placed in cell culture. By subsequent selective transfer of epithelial cells and maintenance in an atmosphere of 8% CO2, cell lines with characteristics of neuroendocrine cells were established. The neuroendocrine markers expressed by these cell lines included electron dense neuroendocrine secretion granules as well as secretion of calcitonin and mammalian bombesin. In keeping with data previously reported for a human neuroendocrine lung tumor cell line, nicotine, acetylcholine, and mammalian bombesin (MB) acted as strong growth factors in these neuroendocrine hamster tumor lines. The mitogenic effect of nicotine and acetylcholine was abolished by nicotinic receptor inhibition while the effects of mammalian bombesin were inhibited by an antagonist of MB receptors. Our data suggest that a receptor-mediated mitogenic effect of nicotine on neuroendocrine lung cells may be instrumental in the induction of smoking-associated small cell lung cancer.