Three separate evaluations of a computer-assisted instructional (CAI) drill and practice program were conducted. The CAI was provided by the Los Angeles County Superintendent to 14 districts as a means of improving students' math abilities and to help teachers manage diagnostic and prescriptive information. The California Test of Basic Skills (CTBS) and the California Arithmetic Test (CAT) were administered before and after instruction to both experimental (i.e., CAI) and control groups. In general, the results indicated that: 1) the mean post-test scores for the experimental groups exceeded those of the control groups; 2) a higher percentage of experimental than of control students exceeded their expected growth rates for the period; and 3) the students receiving CAI experienced growth rates substantially beyond normal expectations. Control group students performed better on tests of reasoning ability, perhaps because the CAI did not stress this skill. Since the program was of moderate cost, promoted student learning, reduced the teacher's remedial work and aided in diagnosis and prescription of student academic needs, it was recommended that it be expanded. (PB)