A Chemistry Concept Reasoning Test was created and validated providing an easy-to-use tool for measuring conceptual understanding and critical scientific thinking of general chemistry models and theories. The test is designed to measure concept understanding comparable to that found in free-response questions requiring explanations over calculations. The development of the test focused on the design of new multiple-choice questions to challenge and determine students' understanding by providing various types of questions that require visualization, logical reasoning, and particulate explanations. Validation was achieved in several ways. The primary validation of the Chemistry Concept Reasoning Test was done in a General Chemistry course through correlation with students' scores on a free-response final exam and total scores in the overall course. High Pearson product moment correlation coefficients for each version of the test and relationship provide criterion-related convergent validity. (Contains 1 note, 1 table, and 2 figures.)