The one group posttest only evaluation model has been identified as a relatively inexpensive and useful model that can identify program components that are not being successful. The use of the model is discussed and illustrated through a hypothetical evaluation of a compensatory (Chapter 1) program. The one group posttest only evaluation model makes it possible to evaluate a compensatory program when there is no available comparison group and no pretest data are available. The design is valuable for three reasons: (1) evaluators seldom, if ever, find a perfect comparison group; (2) it can be very difficult to find a test that serves as a pretest and can also measure the objectives adequately at posttest; and (3) the design allows for identification of the components of the program that are not successful, providing guidance for program improvement decisions. Two tables and five figures illustrate the discussion. (SLD)