Fluoxymesterone (Halotestin) is an anabolic steroid with strong androgenic properties that has been used in the treatment of male hypogonadism, delayed puberty in males, and in the treatment of breast neoplasms in women. It is approximately 5 times as potent as methyltestosterone. The antitumour activity of fluoxymesterone appears related to reduction or competitive inhibition of prolactin receptors or estrogen receptors or production.

Like many C-17 alpha alkylated steroids, Fluoxymesterone (Halotestin) has poor binding to the AR. Even so, its actions are mediated by the androgen receptor, most-likely due to its prolonged plasma half-life.

In some circles, it is claimed that fluoxymesterone is only useful to a small select group of athletes who seeks very specific goals. Athletes tend to use it to increase strength and aggression in the gym or in competitions such as strongman contests, fighting (like boxing) or mixed martial arts - MMA. The lack of estrogenic activity makes Halotestin perfect for pre-fight usage – as weigh-ins would not be effected by water retention. Even in such an events, Fluoxymesterone usage is usually limited to mere few weeks rather than cycled like real steroids for months. It is considered a very toxic oral drug.

The half life of Fluoxymesterone (Halotestin) is commonly misunderstood. The rumored belief is that 30-90 minutes is the half-life but this rumor is false, the half life of Fluoxymesterone is about 9.2 hours.