The importance of selection criteria for choosing participants in a career criminal program is emphasized, and some criteria for the selection process are suggested. The study assessed the possible impact on arrests of a career criminal program in the District of Columbia had one been initiated in 1972 and 1973. A cohort of 4,703 defendants was established. The criminal histories of the subjects were known for a 56-month period during which a career criminal program was not in effect. The official criminal behavior of the cohort group and the time they were incarcerated were combined to calculate an 'arrest rate' for each of the defendants. This information was used to calculate the reduction in arrests that might have been achieved with a career criminal program. The study allowed three characteristics of this hypothetical career criminal program to vary: the size of the target group, the method of choosing participants for the program, and the conviction rate that could be achieved with the cases assigned to the career criminal unit. A table indicates the expected percentage reduction in adult arrests which, depending upon the variables, ranged from 19 percent to 1 percent. The discussion of developing criteria that will enable a career criminal program to have an effect on future crime analyzes four studies that together present a picture of career criminals that is relatively consistent. In general, the studies indicate that property crimes seem to be better predictors of future criminality than violent crimes with no property motivation. Other factors to consider are unemployment, drug and alcohol abuse, and age. Two tables and 14 footnotes are supplied.