The effectiveness of videotape feedback, verbal feedback, and a combination of videotape and verbal feedback upon the psychomotor performance of 90 borderline, mild, and moderately retarded adolescent students in a residential school was compared. The students were divided into a high intelligence group and a low intelligence group and then randomly assigned in groups of 15 to the videotape, verbal, and combination conditions. A mailing task involving envelope stuffing was demonstrated to each student by videotape, after which the student was asked to perform the psychomotor task. Measures of performance were the student's scores for the first and last trials of the task and the total number of envelopes stuffed in 30 minutes. Covariant and two-way analysis of the students' scores on the envelope stuffing and two-way analysis of variance for number of envelopes stuffed during the three conditions indicated that the verbal feedback group performed significantly higher than the other groups, that there was no difference in number of envelopes stuffed by the groups, and that the high intelligence groups stuffed a larger number of envelopes than the low intelligence groups. (Author/MC)