The Flows and Costs model emerged from an increasing recognition of the importance of costs in criminal justice policy appraisal. The model provides a systematic framework -- but not a mechanical device -- for estimating the "downstream" effects of policies introduced earlier in the criminal justice process. One of the tables presented in this report summarizes the costs of dealing with an individual for a "typical" offense, as he/she proceeds through the criminal justice process. Pretrial costs include Green Form legal aid, police case preparation, and police station duty solicitor schemes. This table also presents the estimated cost of appeals against conviction and/or sentence and the cost of dealing with offenders who violate community orders. The model shows that the average cost of a magistrates' court proceeding is 550 pounds. The average cost of a magistrates' court sentence is 250 pounds, and the average cost of a prison sentence imposed at a magistrates' court is 4,950 pounds. The average cost of a Crown Court proceeding is 8,600 pounds. The average cost of a Crown Court sentence is 23,900 pounds, and the average cost of a prison sentence imposed at the Crown Court is 30,500 pounds. The average cost per defendant in the courts (including sentence) is 2,700 pounds. These figures include costs to all criminal justice agencies, such as the Legal Aid Board and Crown Prosecution Service. Developments are currently underway to improve the measurement of costs in various parts of the criminal justice process. 3 tables and 2 figures