Attention has recently been focused on the need to design and validate instructional materials that guarantee competent student performance. In preparing such products, developers have come to rely on competency-based achievement tests. Unfortunately, expertise for constructing reliable and valid competency-based instruments is not currently available in a form than an instructional developer can readily translate into practice. The formulation of objectives to guide instrument construction is problematic for the developer because few dependable rules exist to help select and state them. Formulating items is also difficult because many developers lack training in test writing. Further, major issues arise when the developer must establish the meaningfulness of the scores that result from competency-based instruments, a difficult and costly task that requires psychometric skill and a generous budget. Finally, a discerning developer knows in advance of instrument validation that little assistance will be available from psychometricians who have long been arguing over the designs and statistics to be used validating competency-based tests. Data derived from competency-based instruments must therefore be used with caution and confirmed with additional sources of information like observations and interviews. Developers should also require test construction and psychometric expertise. (Author)