Long term studies of advance organizers (AO) were analyzed with Glass's meta-analysis technique. AO's were defined as bridges from reader's previous knowledge to what is to be learned. The results were compared with predictions from Ausubel's model of assimilative learning. The results of the study indicated that advance organizers were associated with increased learning and retention of the material to be learned. This was consistent with Ausubel's prediction. However, other variables associated with high "effect size" (ES) were not consistent with predictions by Ausubel's model. Four specific results contradicted the model. These were lower ES's associated with written-only and abstract AO's; higher ES's with non-subsuming AO's; lack of special facilitation for low ability, or low knowledge learners; and lower ES's for older learners. A modification of Ausubel's model may be needed to account for the positive effect of AO's demonstrated in this review. (DWH)