This article is focused on the use of norethisterone acetate as progestogen in hormone replacement therapy. Emphasis is made on the fact that the primary reason for adding a progestogen to hormone replacement therapy is to protect the endometrium against hyperplasia. In this paper we review data that demonstrate that hormone replacement therapy that includes norethisterone acetate has positive effects on the postmenopausal bone metabolism and that it increases bone mass more than expected and more than treatment with alendronate. All available evidence is reviewed to show that norethisterone acetate, if given in the correct dosage, does not influence serum lipids and lipoproteins in any negative way. It is furthermore shown that norethisterone acetate seems to be superior compared to other progestogens to provide optimum bleeding control and endometrial protection. Also, hormone replacement therapy combinations with norethisterone acetate efficiently alleviate hot flushes. Hormone replacement therapy and the risk of breast cancer and the role of progestogens are discussed.