The need to reduce the costs of incarceration to state and federal correctional agencies has allowed the movement to privatize correctional institutions to gain considerable momentum. The empirical evidence regarding whether private prisons are more cost-effective than public institutions, however, is inconclusive. To address this question, a meta-analysis was conducted of 33 cost-effectiveness evaluations of private and public prisons from 24 independent studies. The results revealed that private prisons were no more cost-effective than public prisons, and that other institutional characteristics such as the facility’s economy of scale, age, and security level-were the strongest predictors of a prison ‘s daily per diem cost.