Using blood cultures the response to gamma (γ) radiation was examined in a male DMD and his mother, in a female DMD and her mother and in a normal control. In a series of experiments chromosome aberrations were determined after 3 separate γ-irradiation dose levels: 0, 150, 300 rads. The DMD patients showed a response to ionising radiations different from control, in fact the percentage of aberrations was lower than the control. In this preliminary study a slight difference between normal and possible carriers was also found.