This study examined the effectiveness of a computer-based learning system designed specifically to provide individualized spelling instruction. The principal focus of this study was to determine this system's effectiveness in promoting spelling achievement among third- and fourth-grade students;An experimental design approach was used in this study to compare the performance of students working in a teacher directed individualized spelling program with the performance of students working in a computer-based individualized spelling program. One hundred sixty-three third- and fourth-grade students and their teachers from a midwestern suburban school district comprised the sample population;Pre- and postassessments of student spelling achievement and attitude were given, as well as a retention achievement test administered six weeks after the completion of the experiment. Teachers were asked to record daily the amount of instructional time they devoted to each instructional program. These data were collected during the spring semester of 1981. (1) The computer-based students' postexperiment and retention test achievement scores were significantly higher than the scores of the students working in the teacher-directed program. (2) There was no interaction between the type of instructional program and spelling ability. There were no significant differences in the spelling growth rates among the ability groups within each program. (3) The changes in student attitude toward spelling did not differ significantly between instructional programs. (4) There was a significant difference in the amount of time teachers invested in the two instructional programs. Teachers used three times more instructional time in the teacher-directed program than they did in the computer-based program. (5) The rate at which students encountered unfamiliar words in the computer-based program could be increased at least a third without significantly affecting their posttest achievement scores.