Metallothionein (MT) is a low molecular weight protein, which participates in differentiation and proliferation of normal and tumour cells. In some malignant tumours (mammary, renal, ovarian cancers), its increased expression is thought to represent an unfavourable prognostic factor. Non-small-cellular lung cancers (mainly squamocellular cancer and adenocarcinoma) are characterised by ill-defined prognosis, which poses problems in the selection of effective post-surgical therapy. The present study aimed at demonstration of the prognostic significance of MT expression in cells of non-small cell lung cancers, attempting to correlate the intensity of MT expression with G grade and with the intensity of proliferation-associated antigen, Ki-67 expression. The studies were performed on archival paraffin blocks with samples of 25 cases of non-small cell lung cancers (5 squamous cell cancers, 20 adenocarcinomas). In paraffin sections of the studied tumours, immunocytochemical reactions were performed, using mouse monoclonal anti-MT and anti-Ki-67 antibodies. The expressions of MT and Ki-67 were demonstrated in all the studied tumours. An analysis of correlation between the expression of MT, Ki-67 antigen and G grade demonstrated a strong positive relation between the latter two parameters (r=0.70; p<0.05). Less pronounced positive correlations were disclosed between MT expression and G grade (r=0.44; p<0.05) and between MT expression and the expression of Ki-67 antigen (r=0.41; p<0.05). In addition, in 15 cases of examined tumours, survival analysis was performed, which disclosed a shorter survival in patients with high MT expression. The obtained results confirmed the relationship between MT expression and Ki-67 antigen expression, indicating an involvement of the proteins in processes of tumour cell proliferation. In turn, the shorter survival of patients with high expression of MT pointed to prognostic significance of the protein in non-small cell lung cancers.