Selective androgen receptor modulators or SARMs are a novel class of androgen receptor ligands. They are intended to have the same kind of effects as androgenic drugs like anabolic steroids but be much more selective in their action, allowing them to be used for many more clinical indications than the relatively limited legitimate uses that anabolic steroids are currently approved for.
SARMs provide the opportunity to design molecules that can be delivered orally, but that selectively target the androgen receptors in different tissues differently. The goal of research in this area is to allow a customized response: Tissues that are the target of the therapy will respond as they would to testosterone; other tissues where undesirable side-effects are produced will not.

Several SARMS nonsteroidal androgens show a ratio of anabolic to androgenic effects of greater than 3:1 and up to as much as 90:1 (RAD-140), compared to testosterone, which has a ratio of 1:1.