AIM:   This paper is a report of a clinical trial of the effects of music therapy on anxiety of female breast cancer patients following radical mastectomy. BACKGROUND:   There is insufficient evidence on the effects of music therapy on state anxiety of breast cancer patients following radical mastectomy. METHODS:   A Hall's Core, Care, and Cure Model-based clinical trial was conducted in 120 female breast cancer patients from March to November 2009. A randomized controlled design was utilized. The patients were randomly allocated to the experimental group (n = 60) received music therapy in addition to routine nursing care, and the control group (n = 60) only received routine nursing care. A standardized questionnaire and the State Anxiety Inventory were applied. The primary endpoint was the state anxiety score measured at pretest (on the day before radical mastectomy) and at three post-tests (on the day before patients were discharged from hospital, the second and third time of admission to hospital for chemotherapy respectively). RESULTS:   The pretest score revealed that the majority of the patients had a moderate level (77·5%) and 15% had severe level of state anxiety. The repeated-measure ancova model analysis indicated that the mean state anxiety score was significantly lower in the experimental group than those in the control group at each of the three post-test measurements. The mean difference between the experimental and control group together with 95% confidence intervals were -4·57 (-6·33, -2·82), -8·91 (-10·75, -7·08) and -9·69 (-11·52, -7·85) at the 1st post-test, 2nd post-test and 3rd post-test respectively. CONCLUSION:   Music therapy is found to have positive effects on decreasing state anxiety score.