Abstract: This article studies the implications for the theory of deterrence of (a) the manner in" which individuals' disutility from imprisonment varies with the length of the imprisonment" term; and (b) discounting of the future disutility and future public costs of imprisonment. Two" questions are addressed: Is deterrence enhanced more by increasing the length of imprisonment" terms or instead by raising the likelihood of imposing imprisonment? What is the optimal" combination of the severity and probability of imprisonment sanctions?"