The internal consistency and convergent and discriminant validity of the d2 Test, a cancellation test of attention and concentration, was examined in a sample of 364 U.S. adults. Test-taking strategy, new process scores for assessing performance constancy, and relations to gender and education were explored. Results suggested that the d2 Test is an internally consistent and valid measure of visual scanning accuracy and speed. Overall performance scores were related to a proxy measure of test-taking strategy in the expected direction, and new acceleration and deterioration measures exhibited convergent validity. Suggested directions for future research include discrimination of attentional processes that support immediate and sustained visual scanning accuracy and speed, further examination of the impact of test-taking strategies on overall performance measures, and additional construct validity examinations for the new process measures. (JINS, 2004, 10, 392–400.)