This paper critically examines the inadequacies of sentencing practice in relation to a number of aspects of offender psychology. It Is argued that sentencers are inadequately informed in regard to the two major goals of sentencing: deterrence and rehabilitation. Without conducting thorough evaluations of the effectiveness of sentencing, including an analysis of the experience of offenders, it is likely that ''sentencing in the dark'' will continue. The literature on the perspectives and beliefs of offenders suggests that although offenders may plead guilty in the hope of achieving a lower sentence, in many cases there is likely to be a lack of genuine remorse and therefore the sentencing process will not effectively engage the offender. Similarly, the literature on deterrence suggests that offenders underestimate their chances of getting caught, and this is likely to diminish the intended deterrent effect of sentencing. It is argued that the current arrangement suits both sentencers and offenders as bureaucratic efficiency is served and sentences are ''discounted''. It is suggested that psychology has much to offer the criminal justice system by critically evaluating the likely impact of various sentencing strategies and pointing out conflicts in sentencing practice. The first step, it is argued, should be an attempt to disentangle the confusion of sentencing and treatment that often places both offenders and treatment staff in conflict and compromises the integrity of treatment programs.