Recent studies refuting the effectiveness of advance organizers in preparing students to comprehend text material have not met the conditions necessary for advance organizers to succeed. According to the assimilation theory, which holds that people learn by chaining what is known to what is to be learned, the following conditions must be met for advance organizers to be effective: (1) the material should be new; (2) it should be able to be conceptualized in a meaningful, assimilative context; (3) advance organizers should either give or isolate this meaningful context; (4) advance organizers should actively force their use by learners; (5) learners do not have prior knowledge of the meaningful assimilative contexts and would not regularly use subsumption in learning new materials; and (6) posttests should measure transfer and long term retention. Prose advance organizers may be either expository or comparative. Graphic organizers, which are visual as well as verbal presentations, appear to have a number of advantages over prose organizers. For example, they have been operationally defined, may be constructed with a relatively simple set of directions, and allow for interaction between students and teachers. Used properly, advance organizers can upgrade students' comprehension of textbook material. (MM)