OBJECTIVE To determine if clonidine abuse among non-pregnant opiate dependent individuals is common and the reason for such use. METHODS Self report of personal use or knowledge of others' use of this drug. RESULTS Fourteen of fifteen treatment seeking individuals with opiate dependence knew of clonidine abuse. Ten had used it personally to decrease the amount of heroin necessary to achieve a desired effect and to prolong the length of the opiate's action. CONCLUSIONS Clonidine abuse among opiate addicts may be more common than previous studies have suggested. Opiate addicts should be screened for abuse of this substance, especially in view of its widespread use for the purpose of opiate withdrawal. Further, such patients should be warned of potential health hazards attendant upon clonidine use and abrupt cessation.