Apoptosis (programmed cell death) plays a very important role in the development regulation, homeostasis maintenance as well as in the origin of many diseases, including neoplasms. This process is genetically regulated and reflected in characteristic morphological and biochemical changes taking place in cells. The process is considered to be of great significance in tumour originating and growth as well as in tumour cell response to chemotherapy. There are many genes and their products that are involved in apoptosis. The following genes: p53, bcl-2 and p21 seem to have the greatest significance. Our study aimed at evaluating p53 gene expression in non-small-cell lung cancer patients after neoadjuvant chemotherapy. We examined the tissue material from 35 patients after three-cycle inductive chemotherapy (Vepesid and Cisplatin). The material was obtained before chemotherapy during bronchofiberoscopy and four weeks after drug treatment during surgery. The control group comprised patients who had not undergone inductive chemotherapy. After deparaffinising of tissue slides, gene p53 activity using in situ hybridisation technique was evaluated. Moreover, apoptosis valuation with TUNEL method was performed. The results were documented as photographs. Gene p53 activity level was estimated using cytophotometric technique. Our study revealed significantly higher percentage of cells undergoing apoptosis and increased gene p53 activity in tumour tissue slides of patients after neoadjuvant chemotherapy.