This study is primarily concerned with the phenomenon of citizens who believe they have been arrested and thus may develop a stigmatized self-concept. The subjects consisted of a 10 percent random representative sample of the cohort of 9,945 males born in Philadelphia in 1945 and who lived in Philadelphia at least from the ages of 10 to 18. Only 567 subjects could be reached and interviewed. In comparing the responses of the interviews with their criminal record, seventy-five respondents or 30 percent of the 257 interviewees who described their first arrest did not have any official criminal record. Twenty-nine respondents or 20 percent of the 144 interviewees also described a 'last arrest,' namely they described another offense for which they were supposedly arrested. Official offenders differed significantly from official nonoffenders with regard to race, victimization type, relational distance between complainant and offender, and offense seriousness or complexity. Those who were officially arrested committed more offenses against commercial victims, who are likely to insist on arrest; unofficial offenders committed more offenses with community victims. The results support the proposition that citizens perceive or interpret contacts with the police as arrests, that the behavioral distinction between arrest and other types of police contacts is ambiguous, and that self-reported arrests or arrests as personal experiences are considerably higher than official statistics or records indicate. Tabular data and 57 references are provided.