The definition of marijuana (Cannabis) dependence (addiction) contains three critical elements. These are (a) preoccupation with the acquisition of marijuana, (b) compulsive use of marijuana, (c) relapse to or recurrent use of the marijuana. The manifestations of abnormal marijuana use may assume many forms. Medical, psychiatric, neurological, traumatic, and sociological sequelae occur commonly in acute and chronic marijuana use. Marijuana dependence must be diagnosed primarily as the etiological or precipitating agent to adequately prevent and treat these conditions. The central role of marijuana addiction can be identified. The consequences of the marijuana addiction should be separated from the marijuana addict's actual motivation or craving to use marijuana. Marijuana addicts use abnormally because of what marijuana does to them and not for them. Marijuana reinforces its own use. Psychosocial stressors are not required to produce a marijuana addiction in biologically susceptible individuals. Consequences that result from an addiction to marijuana do not produce the abnormal use. A presumptive diagnosis of marijuana dependence (addiction) can be established by detecting significant consequences associated with marijuana use. A definitive diagnosis entails confirming the presence of addictive behavior by identifying a preoccupation, compulsivity and relapse relative to the drug, marijuana.