The effects of homogeneous ability grouping versus heterogeneous grouping on the reading achievement of 18 slow learners at the first grade level are studied here. Two matched groups, each containing 9 pupils classified as slow learners from reading achievement based on Metropolitan Reading Test scores, are placed in homogeneous and heterogeneous groups and taught by Betts and Welch's basal reading method. Both groups are taught reading 1 hour per day in their respective self contained classrooms, and time allotted on topics is the same. The Metropolitan Reading Readiness Test is administered on a pretest and posttest basis. An analysis of covariance testing the significance between the pretest and posttest means of the two groups indicates no significant difference in reading achievement. The type of grouping used in this study appears to have no effect on reading achievement by these slow learners. Among the differences noted between the two groups are that the means of the homogeneous group are higher than that of the heterogeneous, that the slow learners in the former group tend to show higher achievement in reading readiness than children in the latter group, and that the children in the heterogeneous group are not able to keep the pace designed in the reading format. Some children do not acquire the skills necessary to proceed to a new unit in reading instruction. (Author/AM)