An investigation of biology matriculation tests in Israel was undertaken to assess the use of justifications with multiple-choice items and to compare the effect of three item formats on students' performance. More specifically, the study was designed to determine the: (1) extent to which justifications will differ if the correct answer is made known to the students so that they can concentrate on the justification; and (2) necessity of distractors. Subject samples included 114 tenth and eleventh graders in 7 California high schools in 1987 and 350 Israeli twelfth graders who studied biology toward the matriculation examination in 1987. The same 20 items were presented to the students in three formats--standard multiple-choice, multiple-choice in which the correct answer is marked, and a simple statement of the correct answer without the distractors. Students' justifications for the three item formats were compared, and significant differences were found. Results confirm the usefulness of justifications as a diagnostic tool and indicate the usefulness of future uses of justifications, particularly in the development of two-tier items. (TJH)