In recent years breast-conserving therapy has become the most frequently used therapy for early stages of breast cancer. The complete excision of a tumour using this protocol is a statistically significant parameter which influences the incidence of local recurrence and overall survival. Evaluation of the completeness of the resection and especially the distance of the tumour from the margins of the lumpectomy, however, brings a number of problems which arise not only from the character of the tissue with a majority of adipose stroma, but also from the character of the tumour tissue itself regarding growth pattern and multifocality. In fact, establishing the dimension of the margins which we consider safe, remains rather controversial. In this article we discuss contemporary views on the free or safe margins evaluation and summarise technical possibilities for examination of the resection margins in mammary oncosurgery.