Dysregulation of apoptosis is closely associated with malignant cell transformation. On the other hand, apoptosis is induced by chemotherapy or irradiation. Therefore, in 54 patients with locally advanced non-small cell lung cancer (NSCLC, 36 squamous cell carcinomas, 18 adenocarcinomas, stage IIIA/IIIB), apoptotic indices were comparatively analysed before onset and after termination of neoadjuvant therapy. The results were compared with the response to neoadjuvant therapy (extent of therapy-induced tumour regression) as well as the survival times. A statistically significant difference could not be established between pre-therapeutically and post-surgically established apoptotic indices (mean values: 0.93% vs. 1.1%). Neither before therapy nor after surgery did the apoptotic indices show a significant predictive value concerning different overall survival times. These results suggest that neoadjuvant therapy does not modify the extent of apoptosis in lung cancer in the long term. Only a few weeks after the completion of the neoadjuvant chemoradiotherapy this contributes to a net proliferation of the residual tumour tissue which is largely equivalent to that of the untreated tumour.