The medication modafinil has been shown to reduce cocaine use in some cocaine users. The investigators have shown that modafinil taken in the morning improves sleep in chronic cocaine users. The investigators hypothesize that the beneficial effects of modafinil in reducing cocaine use may be related to specific effects modafinil has on sleep. This study will measure sleep and cocaine use in cocaine dependent persons who are trying to stop using cocaine, and will test the connection between modafinil's effects on sleep and cocaine use.