Data from prison records were collected on a sample of 100 male sex offenders incarcerated in two Scottish prisons to compare the ages and offending histories of those convicted of various types of offenses. Offenses were categorized into those involving rape and those involving other illegal sexual acts; homosexual offenses involving assaults on boys were examined separately. Results showed that rapists were younger and had a less repetitive pattern of offending than those who did not rape their victims, irrespective of whether the victim was a child or adult. Consideration of the nature of the act in sexual offending makes psychological sense in understanding the offender's criminality and psychosexual problems; this type of categorization could be useful in making predictions about an offender's future and in devising treatment strategies. 3 tables, 1 figure, and 11 references