Objective To study the clinical effect of tamoxifen on the treatment of breast cystic hyperplasia.Methods 288 cases of breast cystic hyperplasia were entered randomly as experimental group,it was given tamoxifen 10mg～20mg Bid for 1～3 months;and control group,was given methyltestosterone l0mg Bid,the clinical effect of the two groups was compared.Results In experimental group,the cure rate was 45 5%(131/288),the obviously effective rate was 39 9%(115/288),the effective rate was 12 2%(35/288),and the inffective rate was 2 4%(7/288),the total efficiency was 97 6%(281/288),while the total efficiency in control group was 88%(132/150).There was significant difference in the two groups(P