The cost and effectiveness of computer-based instruction for military training are evaluated on the basis of about 30 studies conducted since 1968. Four methods of instruction are distinguished and compared: Conventional Instruction, Individualized Instruction, Computer-Assisted Instruction (CAI) and Computer-Managed Instruction (CMI). Student achievement at school is about the same with all methods of instruction. CAI and CMI save about 30 percent (median) of the time required by students to complete the same course given by conventional instruction. Individualized instruction (without computer support) also saves student time; the addition of CAI or CMI to courses taught this way saves little additional student time. Student attrition appears to increase with CMI compared with conventional instruction, but changes in student quality may also account for this increase; no such data are available on CAI. Students prefer CAI or CMI to conventional instruction; attitudes of instructors, considered in only a few studies, are unfavorable to CAI and CMI. Direct comparisons of the cost and effectiveness of different methods of instruction are not now possible because of incomplete cost data. Most so-called cost savings attributed to CAI and CMI are based on estimates of pay and allowances of students for the time saved by these methods of instruction; data for other costs, such as for CAI or CMI equipment, courseware and instructors must also be considered.