The actual impact of cognitive theory on testing contrasts sharply with its potential impact, which suggests some deep incompatibilities between the areas. This article describes and illustrates a cognitive design system approach that centralizes cognitive theory in developing valid tests. To resolve incompatibilities between cognitive and testing, the cognitive design system approach includes both conceptual and procedural frameworks. To illustrate the cognitive design approach, an item bank for measuring abstract reasoning was generated from cognitive theory (i.e., P. A. Carpenter, M. A. Just, & P. Shell's, 1990, processing theory). The construct validity of the generating item bank was strongly supported by several studies from the cognitive design system approach.Developing tests from cognitive theory has been an intriguing possibility for psychological and educational measurement (Embretson, 1985;Mislevy, 1993;Wittrock & Baker, 1991). Many item types that appear on tests have been studied by contemporary cognitive psychology methods. Often, ability test item types are suitable for studying cognitive theories, because they are complex problem-solving tasks.Despite the interest in cognitive theory, its purported promise for test development is barely realized. Certainly, contemporary cognitive concepts are often used to describe traditionally designed measures. Various ability test scores are described as reflecting parallel versus serial processing, cognitive consistency, executive processing, and so forth (e.g., Kaufman & Kaufman, 1993). However, as noted by Pellegrino (1988), applying cognitive concepts to describe traditional psychometric findings misses the real potential of cognitive theory; namely, cognitive theory is useful for test design. Cognitive psychology research has an incidental bonus for test design, because justifiable operational definitions are required for construct measurement. The specific operations are often detailed descriptions of task stimulus properties. Thus, cognitive research also provides results