[en] The effect of radiotherapy on hemoglobin (Hb) polymer, obtained from patients (cases) before and after two periods of local gamma irradiation was studied. The results were compared with healthy volunteer. The patients were classified into two main groups. The first group represents cases that suffer from breast cancer, while, the second group represents cases that suffer from pelvic cancer. The total doses for breast cancer were ranged from 45 to 50 Gy, divided into 25 fractions for 5 weeks. While the total doses for pelvic irradiation were ranged from 20 to 66 Gy; divided into 10-25 fraction for 2-5 weeks. The physical properties of Hb have been studied via several characterization techniques, such as X-ray diffraction, viscosity, Fourier Transform Infra-red spectroscopy (FTIR), Electron Spin Resonance (ESR) and UV-visible spectra. The resultant effects of radiotherapy can be summarized as follows: X-ray diffraction pattern of Hb polymer, for control and cancer breast before and after exposure to accumulated gamma irradiation, were characterized by halo consisting of two adjacent peaks with maximum intensity observed at 2θ = 9.549 and 21.222, respectively. By increasing the gamma doses, a decrease in crystalline phase (disordering character) were obtained. Also, the halos width at half of maximal intensity (δW) shows a decrease followed by an increase with increasing the accumulative gamma dose up to 50 Gy, but still below + ve and -ve control values. The viscosity were measured for Hb solutions of concentration 4.1x10^-5 Mol on the base of heme-heme interaction and at different shear rates (10-400 sec^-1). The plastic viscosity for every hemoglobin samples was calculated by Bingham equation using specific software of the viscometer. There was an increase in the plastic viscosity of Hb cancer patients compared to -ve control. On irradiation the viscosity shows an increase with increasing the accumulative gamma dose. Fourier transform infra-red spectra (FTIR) indicated that there is a decrease in intensity of all Hb amides for cancer patients with the radiotherapy. Local irradiation caused a decrease in intensity of amides, indicating some destruction of amides bonds at the mid of accumulated doses. At the end of irradiation there is an increase in intensities which means more association of bonds (cross-linking). These cross-linking achieved also in the cases of pelvic irradiation on radiotherapy. Electron spin resonance (ESR) was performed for the lypholized Hb samples and the number of free radicals was calculated. The number of free radicals for all cancer patients was increased over the range of negative control. On radiotherapy the number of free radicals increases at the end of irradiation. Hb solution samples were adjusted at concentration of (2.6x10^-5 mol) on the base of globin band at 275 nm using distilled water, recorded from (200-700 nm) using UV-Visible spectrophotometer. There is an increase in absorption in breast cancer globin-heme interaction band for positive control compared to negative control. For soret band, there is a decrease in absorption of soret band for the + ve control than the value of -ve control. While, on irradiation there is an increase in absorption with increasing of doses