Studied was the effect of advance organizers, as defined by Ausubel, on the learning of concepts in science. Sixth grade classes studied two sequences of major concept-centered learning tasks developed by the investigator. The first had 12 lessons about energy forms and transformations; the second had five about photosynthesis and respiration as components of cell metabolism. Prior to each learning task the experimental classes were presented with an advance organizer. The first organizer introduced the principle of energy conservation to aid in learning subsequent material. The second organizer, presented between the learning tasks, explicitly related the two learning tasks. Evidence was inconclusive regarding the general role of advance organizers, though it appeared that the advance organizers facilitated learning when pupils lacked the analytic ability necessary to reorganize information independently into suitable clear, inclusive and stable cognitive structures. The study also showed that science information considerably beyond usual limits of elementary school curriculum is within the information processing capabilities of sixth grade pupils when it is presented in carefully structured and sequenced form based on major science concepts. (GR)