Serum haemoglobin has been shown to be an independent prognostic factor for a number of cancers including head and neck, bladder, cervix and anal cancers. This study has investigated the prognostic significance of pre-treatment haemoglobin in 164 consecutive patients receiving radical radiotherapy for non-small cell lung cancer. Forty-six received conventional fractionation to 60 Gy in 30 fractions and the remainder received accelerated fractionation, either CHART, 54 Gy in 36 fractions over 12 days (27 patients) or CHARTWEL, 60 Gy in 40 fractions over 18 days (76 patients). Patients were divided into three equal groups by haemoglobin concentration. The median overall survival in each of the three groups from lowest to highest haemoglobin was 17.5 months (95% CI 7.9 25), 18.4 months (95% CI 15.0 25.9) and 16.3 months (95% CI 13.0-19.6). No significant effect of pre-treatment haemoglobin concentration was seen in predicting overall, local disease free or metastases free survival.