They argue that there are a number of other factors at play that are not often considered by critics (e.g. the sentencing practices of courts) and which, if taken into account, could explain the assumed failure of alternatives to check the prison population. In order to demonstrate the point that some alternatives to custody may be successful in diverting some offenders from custody, they examine the workings of a probation day center which operates as an alternative to custody under the provision of the Criminal Justice Act 1982, Schedule XI 4 (B). 3 tables, 2 notes, 66 references. (Author abstract)