Primary tissue cultures of human lung tumors were prepared from 30 cases of which 16 were diagnosed as squamous cell carcinoma, six adenocarcinoma, four adenosquamous cell carcinoma, three large cell carcinoma, and one small cell lung carcinoma. Chromosomal abnormalities were observed in 26 cases by cytogenetic studies with a GTG banding technique. Specific chromosome bands frequently involved in structural abnormalities were seen on 1p11, 1q11, 2p10, 6p10, 7q11, 7q22, 7q32, 8q22, 9q22, 11q11, 21q10, and Xq24. We assumed that especially i(2)(p10), i(9)(p10), i(21)(q10), t(11;12), t(14;15), del(X)(q24), and loss of the Y chromosome may play a role in the development of lung cancer as secondary changes. In this way, our cytogenetic findings provide evidence that multiple genetic lesions are associated with the pathogenesis of lung cancer.