Norgestrel,(+) (dextronorgestrel) is the biologically inactive isomer of norgestrel. Dextronorgestrel showed no ability to displace labelled levonorgestrel from the sex hormone binding globulin sites. In vitro active form being converted mainly to the 16 beta-hydroxysteroid and inactive form to the 16 alpha-hydroxysteroid. There was practically no binding to dextronorgestrel of dextronorgestrel to a cytoplasmic receptor prepared from the myometrium of estrogenized immature female rabbits was investigated. While some medications may contain dextronorgestrel, they are often labeled in terms of their levonorgestrel content only, ignoring the inert isomer.