While more than three-fourths had used drugs at some time in their lives, only one-fourth of the drug users had ever been in a drug treatment program. Marijuana was by far the drug most commonly used by inmates, with about 75 percent of the inmates having used it at some time. Inmates were about twice as likely as the public at large to have used drugs. Half of all drug offenses were committed under the influence of drugs -- a fifth under the influence of heroin. The more convictions inmates had on their records, the more likely they were to have taken drugs during the month before their offense. Persons whose offenses were drug related were the least likely to drink heavily during the year prior to their offense among the most likely to abstain altogether. Murderers, rapists, and violators of the public order were the least likely to have been under the influence of drugs at the time of the offense, while drug offenders and burglars were the most likely. Footnotes, graphic and tabular data, and a reading list are included.