The Mathematics Basic Skills Development Project served 15 secondary school locations in the Minneapolis Public Schools' Target Area in 1972-73. The objectives of this project were to develop and use an instructional system which would enable low achieving secondary students to learn basic mathematical concepts and skills. An instructional unit was to be considered successful if over 50 percent of the students who studied it achieved mastery (85 percent or more correct) on a criterion-referenced posttest. Instructional materials to be used in an individualized setting for the remediation of deficiencies in mathematics basic skills were developed, revised, and produced by the project following precise behavioral objectives. In this third year of the project, 2,128 secondary students and 38 teachers made use of the project's revised materials. Four instructional units were given preliminary trials, and revision was indicated for two of the four units. More than 2,100 students completed 6,937 units in 11 instructional areas. Over 50 percent of the students completing units in each area achieved mastery as shown by criterion-referenced posttests. Percents of students achieving mastery ranged from 52 percent in Area Measurement to 85 percent in Dividing Fractions. These were all students who had been below the mastery level on diagnostic tests of these mathematics basic skills. Recommendations are given. (Author)