This article evaluates the role of probation during the period in which the incarceration rate grew at an alarming rate. Sections discuss: the historic link between prison and probation; an explanation of the rise (and potential reversal) of mass incarceration; perspectives on probation-according to the policy arena and to critical academic scholarship; the paradox of probation-serving as both an alternative to prison and as a factor in the growth of incarceration; measuring the probation-prison link outcomes-national and state-level analysis; and the paradox of probation and recent downsizing. “The results suggest that probation was not the primary driver of mass incarceration in most states, nor is it likely to be a simple panacea to mass incarceration. Rather, probation serves both capacities, acting as an alternative and as a net-widener, to varying degrees across time and place ... When combined with other key efforts, reforms to probation can be part of the movement to reverse mass incarceration” (p. 51).