Aim: To conduct single arm prospective trial to assess the feasibility and tolerability of hypo-fractionated post mastectomy radiotherapy. Objectives: To study the tolerability of hypo-fractionated post- mastectomy radiotherapy in terms of acute toxicities, especially dermatitis. Feasibility in terms of target coverage and dose limits to organs at risk were studied. Methods: A single arm prospective study was done on patients diagnosed to have carcinoma breast with indications for post mastectomy radiotherapy and are willing for 3D Conformal Radiotherapy. The dose delivered was 40Gy in 15 fractions to chest wall alone or chest wall and supraclavicular regions. Weekly clinical examinations were done to assess toxicities. DVH data were collected to study the influence of regions treated on CTV coverage, dose to organs at risk. Data entry was done in Micrsoft Excel and analysed using SPSS 16.0. Frequencies and percentages were calculated for discrete variables. The association between the outcome variables was tested using Chi square test. Results: 8.3% of patients developed Grade III dermatitis. None of the patients developed Grade IV toxicities. It was noted that the median V10Gy (26.1 % vs 16.9 %, p value 0.003) and V12Gy (25.2 % vs 16.23 %, p value 0.003) for ipsilateral lung was significantly high when there was addition of supraclavicular field. Conclusion: Hypofractionated radiotherapy is a tolerable treatment regimen. Obese, left-sided breast cancer patients who require supraclavicular irradiation may benefit from IMRT.