Clonidine was administered to nineteen patients in an inpatient setting after abrupt discontinuation of chronic opiate addiction (morphine, héroin, dextromoramide). Clonidine produces a decrease sometimes very rapid in opiate withdrawal signs but does not suppress the whole affects associated with. These data support the hypothesis that clonidine has antiwithdrawal effect by replacing opiate-mediated inhibition with alpha 2 mediated inhibition of brain noradrenergic activity.