The aim of the study was to analyze the prognostic significance of hemoglobin (Hb) concentration for loco-regional control and survival of patients with inoperable carcinoma of the oropharynx. Seventy patients with inoperable squamous cell carcinoma of the oropharynx were prospectively treated by concomitant regimen of conventional radiotherapy and chemotherapy with Mitomycin C and Bleomycin. The prognostic value of Hb concentration before the therapy (Hb-S) and at the end of the therapy (Hb-E), the difference between both (DHb), and the average Hb concentration (Hb-Av) were analyzed. Hb concentration was falling significantly (median values, from 139 g/L to p<0.0001) during the first three weeks of the therapy; after that, it reached a plateau. In the last week of therapy, a slight increase (p=0.08) in Hb concentration was recorded. Significant correlation (p<0.0001) was found between Hb-S and other Hb-related parameters. The median follow-up of the patients alive on close-out date was 5.7 years (range 4-10.5 years). Longer disease-free survival (DFS) and disease-specific survival (DSS) correlated with higher values of Hb-S (p=0.0005, p=0.008) and Hb-E (p=0.02, p=0.02), while the Hb-Av was predictive for DFS only (p=0.004). The most significant difference between low- and high-Hb groups was calculated at cut-off concentrations of 122 (Hb-S), 116 (Hb-E), and 120 (Hb-Av) g/L. Only Hb-S was tested in multi- variate model where its independent value for predicting both, DFS (p=0.002; RR 3.6) and DSS (p=0.01; RR 2.9), was confirmed. In our patients, Hb-Swas proved to bean independent prognostic factor in predicting DFS and DSS. We believe that the concentration of Hb > or =120 g/L should be maintained during radiotherapy course.