Changes in ovarian hormones across the menstrual cycle impact responses to cocaine in women. Studies have shown that cocaine's effects are dampened during the luteal phase of the menstrual cycle, when estrogen and progesterone concentrations are high, relative to the other phases of the cycle, when concentrations of these hormones are relatively low. The purpose of this study is to determine whether progesterone reduces subjective and physiological responses to cocaine in cocaine dependent individuals. In addition, this study will help to advance the possibility of hormonal progesterone and pharmacologically related drugs as potential treatment components for cocaine abuse.