Epidermal growth factor receptor (EGFR) is one of signalling pathways activated during premalignant proliferative changes in the airway epithelium. However there is no agreement about prognostic significance of EGFR expression in non-small cell lung cancer (NSCLC). Facts mentioned above prompted us to study EGFR expression in the group of 78 surgically treated squamous cell lung cancer (SqCLC) patients. The EGFR expression was visualized in formalin-fixed, paraffin-embedded sections, using immunohistochemistry. Three methods of assessment of EGFR expression were applied: percentage of cells with membranous EGFR expression--EGFR labellig index (EGFR LI), percentage of fields with membranous EGFR staining (PS%) and staining intensity (absent, weak or strong) in the whole specimen (SI). Mean EGFR LI and PS% values were 30.4 +/- 3.5% and 51.6 +/- 3.9%, respectively. Patients with higher EGFR expression (EGFR LI, PS%, SI) were significantly younger than those with low EGFR expression. EGFR LI was higher in pT3 tumours than in pT1+pT2 tumours, moreover, EGFR expression (EGFR LI, PS%, SI) was significantly higher in G1+G2 tumours than in G3 tumours. There were significant correlations between parameters used for assessment of EGFR expression. PS% < or = 50 indicated shorter disease-specific survival than PS% > 50. However, patients with tumours with both very low and very high EGFR LI (13% > or = EGFR LI > 80%) showed significantly shorter survival than those with medium EGFR LI (13% < GFR LI < or = 80%). Additionally, pTNM and pN significantly influenced patients' survival. In multivariate analysis, EGFR LI and pTNM were independent prognostic parameters influencing disease-specific survival of patients.