The occurrence and possible implications of an inflammatory state during radiotherapy, as well as the influence of supplementation of the antioxidant amino acid N-acetylcysteine (NAC) were investigated in a prospective randomized double-blind study of 56 patients with cervix cancer referred to radiotherapy. Patients were randomized to receive NAC or a placebo. Erythrocyte sedimentation rare (ESR) changes were representative of those seen with other acute phase markers, and increased in control but not in NAC patients. Red blood cells (RBC), white blood cells, lymphocytes and platelets decreased in both groups but less in NAC-managed cases. In both circumstances, matrix analysis revealed that RBC reductions were inversely proportional to ESR elevations, and a similar tendency was identified regarding lymphocytes.