The study sought to distinguish offenders who lead crime-filled lives that spanned many years from offenders whose criminal careers were of a shorter duration. For this reason, only inmates who were at least middle-aged (40 or older) when last admitted to prison were selected from the initial sample. In the survey there were 827 who entered prison in middle age; statistically weighted, they represent an estimated 24,398 inmates. The study's most surprising finding was that inmates with the shortest record (imprisoned only in middle age) constitute the single most prevalent type of middle-aged inmate. To account for it, the theory of retributive social-debt justice was invoked, together with the assumption that a great many middle-aged men with criminal records had ended their criminal careers by age 40. Tabular data, 20 footnotes, and 20 references are given.