A discussion of evaluating informal logic competence centers on the identification of currently available tests and on a description of test theory, to aid in test selection. The following concepts in test theory are discussed: norm-referenced and criterion-referenced tests, true scores, reliability, validity, test selection and evaluation, test construction, and test format. The use of tests to assess student performance and in various experimental designs is also explained, as well as responsive evaluation, semi-structured evaluation, surveys and questionnaires, and longitudinal follow-up studies. (MH)