It has been widely espoused that there is a link between drug and alcohol consumption and criminal behavior. However, there is little scientific evidence to confirm this belief. The authors examined the data available from the Computerized Lifestyle Assessment Instrument (CLAI), which each offender is asked to complete upon entry to a Canadian penitentiary. Data from 503 offenders were examined, which provided information about the everyday life of offenders prior to incarceration, including information regarding health, relationships with family and friends, and alcohol and drug consumption. Offenders’ criminal histories were also analyzed. The remainder of the article sketches a profile of the alcohol and drug use among these inmates and analyzes the connection between drug use and criminal behavior. Results indicate that offenders consume large amounts of psychoactive substances, although alcohol was the most prevalent drug among the sample. Half of the offenders had used drugs or alcohol on the day they were arrested for their current offense, with cocaine being the most prevalent drug used on their arrest day. The authors assert there is a relationship between drug and alcohol use and violent crimes. It is important to note that many of the offenders stated they would have committed the same crime had they not been under the influence of alcohol or drugs. Financial difficulties were also associated with crimes; in many cases criminality became a way to obtain expensive drugs such as cocaine. As such, while there is a connection between drugs and alcohol and criminal behavior, the relationship assumes many forms. Table, notes