The authors describe the various tests of competency to consent to treatment used today, which include the following: 1)evidencing a choice, 2)"reasonable" outcome of choice, 3)choice based on "rational" reasons, 4)ability to understand, and 5)actual understanding. They analyze the applicability of these tests to patients' decisions to accept or refuse psychiatric treatment and illustrate the problems of ap-lying these tests by citing clinical case examples. They find that the circumstances in which competency becomes an issue determine which elements of which tests are stressed and which are underplayed.