Learning and retention may be influenced by subtle instructional stimulus characteristics and certain visual memory aptitudes. Ten stimulus characteristics were chosen for study; 50 sequences of programed instructional material were specially written to conform to sampled values of each stimulus characteristic. Seventy-three freshman subjects received the 50 sequences and then took an immediate and a delayed (one-week) posttest to assess learning. Measures on four visual memory and cognition aptitude factors were available for 43 of the subjects. By means of tear-down regression algorithms, the 10 stimulus characteristics were used to predict to the learning criteria. The ratio of examples within a sequence to the number of frames in the sequence had a correlation of about -.70 with both the immediate and delayed posttest. The inclusion of other variables did not increase the prediction significantly. Together, total frames and number of responses per frame predicted item difficulty on the posttest (multiple R to the second power=.90). Of the aptitude variables, Vocabulary aptitude and Short Term Object Memory tended to increase prediction to the delayed posttest criterion, while Serial Integration aptitude and short Term Color Memory did not. (LS)