Assessed were the effects of linear and modified linear programed materials on the achievement of slow learners in tenth grade Biological Sciences Curriculum Study (BSCS) Special Materials biology. Two hundred and six students were randomly placed into four programed materials formats: linear programed materials, modified linear program with remedial terminology branches, modified linear program with relationship remedial branches, or modified linear program with both terminology and relationship remedial branches. Units I and II of the BSCS Special Materials were used during the study. Pretest scores on Units I and II were related for all four groups to determine initial differences. The conclusions drawn from the analysis indicated that the modified linear formats terminology and terminology/relationship were the most effective formats in terms of achievement when considering both units. Modified linear format was the most effective when considering the sex of the student and the sub-test scores of Unit II. (Author/PS)