The five criteria discussed pertain to statistical conclusions validity, internal validity, construct validity, external validity, and descriptive validity. Statistical conclusion validity is concerned with whether or not the presumed cause (CCTV) and the presumed effect (crime rates) are related. The main threats to statistical conclusion validity are insufficient statistical power to detect the effect and the use of inappropriate statistical techniques. Internal validity refers to the correctness of the key question about whether the intervention (CCTV) really did cause a change in the outcome (crime rate), and it has generally been regarded as the most important type of validity. In investigating this issue, some kind of comparable control condition is essential in order to estimate what would have happened to the experimental units (people or areas) if the intervention had not been applied to them. External validity refers to the generalizability of causal relationships across different persons, places, times, and operational definitions of interventions and outcomes. The main threats to external validity are interactions of causal relationships (effect sizes) with types of persons, settings, interventions, and outcomes. Descriptive validity refers to the adequacy of the presentation of key features of an evaluation in a research report. This article advises that the quality of CCTV evaluations can be assessed by using the Maryland scientific methods scale. The minimum acceptable evaluation design is to have before-and-after measures of crime in experimental and comparable control areas. Desirable features of future evaluations include using several experimental and control areas; conducting a randomized experiment; conducting surveys of potential victims and potential offenders; having a long time-series of crime rates before and after CCTV; measuring displacement and diffusion of benefits by using adjacent and nonadjacent control areas; testing hypotheses about mediators and moderators; carefully measuring features of the CCTV scheme and features of persons and settings; having independent evaluators; and conducting cost-benefit analysis. 22 notes