The aim of our study was to estimate the expression of the Bcl-xL gene, a member of Bcl-2 family, in NSCLC patients. A total of 60 consecutive patients diagnosed with NSCLC that underwent chemotherapy prior to surgery were reviewed. Bcl-xL expression was assessed on paraffin sections by in situ hybridization (ISH) and immunohistochemistry (IMH). We observed the presence of mRNA of Bcl-xL gene and its protein product overexpression in most patients (60 and 81.7%, respectively). In material examined no significant correlation was observed between the pattern of Bcl-xL or protein expression and any clinicopathological factors evaluated. The expression of Bcl-xL protein was low (less than 10% positive cells) in 11 patients (median survival time 29 months) as compared to 49 patients with overexpression (median survival time 21.0 months). The difference was not of statistic significance (p=0.27). In examined group the Bcl-xL mRNA was found in 36 patients, while it was absent in 24 cases. Median survival time was 14.5 and 86.5 months, respectively (p=0.001). In addition, 19.4% of 5-year survivals were achieved in patients with overexpression and 54.2% in patients with no mRNA present (p=0.002). The percentage of 5-year survival in patients with protein expression assessed by IMH was 30.6% (p=0.31). The estimation of Bcl-xL expression on mRNA and protein level was compared by the means of sign test and the significant difference was found (p=0.009). The inconsistency was related to 35% of cases. In comparison with IMH, ISH technique appeared to be more specific and accurate in assessment of 5-year survival (25 and 65%; 65 and 70%, respectively). The results of our study indicate that Bcl-xL mRNA overexpression may suggest poor prognosis in NSCLC.