The mutations of p53 tumoral suppressor gene are the most frequent genetic modifications identified till now in lung cancer, suggesting that these alterations represent critical stages in malignant cellular transformation of respiration ways. Conformational changes induced by these mutations are associated with stabilisation of the product of p53 gene and the accumulation of the mutant protein in malignant cells' nuclei, in quantities that can be immunohistochemically detected: immunohistochemistry can be used as an indirect indicator of the genome alteration. Eight cases of lung adenocarcinoma were immunohistochemically analysed (formalin-fixed and paraffin-embedded specimens), in order to find the p53 suppressor expression. The overexpression of p53 protein was detected using an antigenous system and Monoclonal Mouse Anti-Human p53 protein, and it was detected in 5 (62.5%) of the 8 examined adenocarcinomas. In the examined cases, p53 overexpression was limited only to neoplastic cells, the nuclear staining being considered specific. p53 high level was correlated to: histological differentiation degree, smoking, the stage of the tumor and to the survival rate of the patients. The association of smoking with p53 overexpression suggests that p53 gene is a target of specific mutagenes in smokers.