Many addicts report on craving--a strong desire to consume the drugs again. Craving is attributed by many addicts to be the main reason for relapse or for the failure to become abstinent. In the recent years some drugs with an "anti-craving" effect have been developed. In this context a review of the complex concept "craving" seems to be urgent. In this paper the psychological conditions of craving and biochemical phenomena possibly underlying craving are reviewed. Basing on the recently available data a new psychobiological concept of craving with two prototypes (craving in early withdrawal and craving during abstinence) has been developed. This model is discussed with regards to possible therapeutic implications.