The aim of this study was to assess the effects of Belladonna 7cH and X-ray 15cH associated in the treatment of acute radiodermatitis. A randomized double-blind placebo-controlled clinical trial involving 66 patients who had been operated on for breast cancer and were undergoing radiotherapy was conducted. The following parameters were assessed over ten weeks: breast skin colour, warmth, swelling and pigmentation. The efficacy of the treatment was assessed by the comparison of these parameters taken individually and by calculating an Index of Total Severity (sum of the scores of the four parameters) during radiotherapy, and during recovery, 15 and 30 d after the end of the radiotherapy. The differences of the scores of the Index of Total Severity during Radiotherapy were not statistically significant, but showed a trend towards a better activity of the homoeopathic medicine compared to placebo. Analysis of the data on Total Severity during recovery, showed a statistically significant benefit of the active medicines over placebo. The homeopathic medicines had particular effectiveness on the heat of the skin. The limited number of patients observed and the posology employed could have interfered with the significance of the results. Chemotherapy and hormonotherapy do not seem to affect the results.