The arrest profile shows the number of arrests accumulated by an individual offender as a function of the age at which each arrest occurred. This provides a summary of the arrest careers of the individuals in the population and facilitates comparisons between groups of interest in the population, such as sex and race groups. In particular, it enables comparisons to be made between cohorts of offenders defined by the age at onset of their offending. For the Western Australia population, large differences are reported between sex and race (aboriginal and nonaboriginal) groups and also between age at onset cohorts. The differences are discussed in the context of current criminological studies that posit higher mean numbers of offenses will be committed by early career starters. Mathematical equations used to assess the precision of the methodology are appended. 26 references, 6 tables, and 12 figures