Official sexual and nonsexual offense histories and confidential self-report data on sexual offending were obtained on 207 adult males serving sentences for sexual offenses against children (98 intrafamilial, 72 extrafamilial, and 37 mixed-type offenders). The mean self-reported age when offenders first had sexual contact with a child was 32.2 years (median = 31 years; range = 10-63 years). The mean age at first conviction for any offense was 30.5 years (median = 27 years, range = 12-66 years), and the mean age at first conviction for a sexual offense was 37.3 years (median = 37 years; range = 15-76 years). Sixty-nine percent (n = 143) of the combined sample had at least one previous conviction, and 80% of these (n = 114) had first been convicted for a nonsexual offense. ANCOVA revealed a systematic pattern of onset with first convictions for any offense preceding first sexual contact with a child. Taken together, results indicate that, in general, adult child molesters (a) begin sexual offending in their 30s, (b) have already become involved in nonsexual crime by the time they first have sexual contact with a child, (c) are criminally versatile, and (d) vary considerably in their persistence with respect to both sexual and nonsexual offending.