Sexual offending is on the political agenda, but there has been little research focus on the four offense categories--indecent assault against a female, indecent assault against a male, indecency between males, and unlawful sexual intercourse with a girl under 16--which together comprise the vast majority of convictions for sexual offenses in England and Wales. The article considers the criminal record (1963-94 inclusive) of the 6,097 males convicted of one of these offenses in 1973. It discusses the results in terms of criminality, heterogeneity, dangerousness, and specialization. By recognizing two levels of analysis--general crime level and sex crime level--the article argues that sex offenders can be both generalists and specialists; they may range widely across a spectrum of offenses but still specialize within sexual offending. Major findings include: (1) Sex offenders differed in their likelihood of being convicted on another occasion; (2) Sex offenders differed in terms of general offending behavior; (3) A significant minority of these offenders were convicted of another dangerous offense against the person during the 32-year observation period; and (4) Sex offenders were much more specialized in their sexual offending behavior than perhaps had been hitherto thought. Tables, notes, references