Trial objectives were to assess effectiveness and tolerance of sterilized Avène thermal spring water anti burning gel (ATSW gel) in prevention of radiation dermatitis in adults irradiated (6 weeks) for breast (n=61) or head and neck (n=8) cancer. Patients included in this open labelled, 2 parallel groups, multicentric study, were randomly assigned to apply five times daily for ten weeks either the Avène spring water gel (n=35) or trolamine cream (n=34). The median of emergence of the first objective radiation dermatitis signs was 31 days in the ATSW gel group and 29 days in the control group (p=0,924). The median incidence for pruritus in patients of the ETA gel group was 46 days versus 27 days (p=0,028) and 44 days versus 24 days for pain (p=0,426). Global efficacy was <<very good>> in 46,7 % of patients of the ETA gel group versus 17,2 % (p=0,029) and tolerance was <<very good>> in 65,5 % of the ETA gel group versus 40,7 % (p=0,107). No radionecrosis was observed. In conclusion, the efficacy of the Avène spring water gel was similar to the control product in prophylaxis of radiation dermatitis. Tolerance was better and the pruritus was significantly more delayed in patients who applied the Avène spring water gel than in controls.