A study involving all students taking the California Achievement Test (CAT) in the Cleveland City School District (Ohio) during the fall of 1989 was conducted to assess the effects of the use of parallel test forms. Each spring, all students in grades 4, 6, and 8 are selected to take the appropriate level of the CAT reading test, Form E. As a result, the question of test familiarity was raised. To address this question, Form F of the CAT battery was selected for administration in the fall of 1989. The sample population included 4,362 fourth, 3,768 sixth, and 2,770 eighth graders. Data from each annual testing from the spring of 1988 through the spring of 1990 were compared with the fall 1989 data. Normal curve equivalent reading scores were used to identify differences between CAT-E and CAT-F scores. To determine whether scores differed significantly for the CAT-E versus the CAT-F, a regression discontinuity design was used to investigate the trends in reading achievement evident for each cohort. Results refute the notion that repeated use of the same form of the test improves scores through "practice effects." The alternative form of the test used during the same academic year provided comparable, or higher, reading achievement levels when used for the first time in the school district. Six figures and one table are included. (TJH)