The 17β-hydroxysteroid dehydrogenases (17β-HSDs) are involved in the regulation of estrogens and androgens by catalyzing the reduction of 17-ketosteroids or the oxidation of 17β-hydroxysteroids. The enzyme activities associated with the different 17β-HSD isoforms are widespread in human tissues, not only in classic steroidogenic tissues but also in a large series of peripheral intracrine tissues. Being involved at the end of steroidogenesis, the numerous members of 17β-HSD family constitute interesting therapeutic targets for controlling the concentration of estrogens and androgens. Thus, inhibitors of reductive 17β-HSD isoforms are attractive to block the formation of hydroxysteroids that stimulate estrogeno-sensitive pathologies (breast, ovarian, and endometrium cancers) and androgenosensitive pathologies (prostate cancer, benign prostatic hyperplasia, acne, and hirsutism). The inhibitors could be used to block the degradation of estradiol, an attractive strategy for treating osteoporosis and Alzheimers disease. In addition to their classical use as anti-cancer agents and therapeutic agents, inhibitors of 17β-HSDs are also useful tools to elucidate the role of these enzymes in particular biological systems. The present review article gives a description of novel inhibitors of 17β-HSDs that were published in 2003-2006.