Advances in the understanding of the biology of lung cancer have progressed rapidly over the past decade while treatment results have remained essentially unchanged. It is clear that the knowledge of the heterogeneity of lung cancer cell types in respect of growth properties, biomarker expression, oncogene expression, and antigen expression needs to be applied in the clinic; and their role in predicting response to cytotoxic therapy and survival needs prospective evaluation. In addition the application of cell lines in screening for tumor-specific cytotoxic agents should provide for a more rational approach for drug selection in future clinical trials. Finally the development of magnetic resonance spectroscopy may also play a role both in further understanding the biology of lung cancer, and in the clinical assessment of tumor sensitivity in vivo. More recent data using DNA probes specific for the cytogenetic deletion on chromosome 3, previously identified in only SCLC, suggests that this deletion 3p 14-23 is common to most, if not all, cell types of lung cancer. This adds further to the hypothesis that a common stem cell exists from which all histologic types of lung cancer arise.