The aromatasum inhibitors of the third generation – letrosol, anastrosol and exemestan are taking the place of tamoxiphen in the case of standard endocrine therapy for women in post-menopause which have breast cancer with positive receptors hormone. Aromatasum inhibitors decrease the level of estrogen by aromatasum inhibition – the ferment that is the catalyst of the last level of the estrogen bio-synthesis. We are observing in this publication the existing proofs of all three agents’ efficiency in case of breast cancer treatment.