In 1986, 20,600 offenders aged 17-20 were sent to prison, a number far exceeding the numbers of juveniles sentenced to immediate custody and representing half the total figure for those over 21 years old. The proportion of young adult males receiving immediate custodial sentences has steadily increased over the past 10 years. There is, however, a disturbing disparity in the sentencing of 17-20 year-olds in both Crown courts and magistrates courts in various jurisdictions. Data indicate that neither offense seriousness nor criminal history provide complete explanations for the greater risk of custody for young adults. There is persuasive evidence that this age group receives harsher sentences because sentencers perceive this group as more unruly, disruptive, and criminally oriented than other age groups. Policy should focus on providing noncustodial alternatives for young adults similar to those for juveniles. This would include alternatives akin to intermediate treatment for juveniles and greater use of probation. 3 tables.