OBJECTIVES: We aimed to investigate the effect of hip prostheses on dose distribution in radiotherapy patients. METHODS: Solid Water phantom-containing prostheses (cobalt-chromium-molybdenum and cobalt-chromium-molybdenum-titanium) were placed between the phantoms used for the measurements. Films at 10, 20 and 30 cm depths were irradiated for 6 and 18 MV with 50 cGy dose in the presence or not of prosthesis. Dose profiles were evaluated statistically. RESULTS: For 6 and 18 MV photon energies, significant differences was found along the thick and vertical axes of both prostheses at 10 and 20 cm depths and along the middle, thick and vertical axis at 30 cm depth (p<0.05). CONCLUSION: Hip prostheses affect radiotherapy dose distribution, and this should be considered when planning a treatment.