40 cases postmenopausal women with breast cancer constituted the study group and 20 sex and age matched formed the control group. The study group of untreated patients showed nonsignificant decrease in molybdenum but significant decrease in blood xanthine oxidase and riboflavin levels. Tamoxifen treated patients showed nonsignificant increase in molybdenum, after 3 months, significant increase after 6 months and significant increase in xanthine oxidase and riboflavin levels. Thus tamoxifen when given in breast cancer helps in amelioration of the diseased condition.