Eleven elementary science texts commonly used in the nation's schools were examined in terms of conceptual structure and reasoning demands of the texts. Specifically, one primary level (K–3) unit was randomly selected for analysis. Concept maps were drawn and evaluated, and the propositions between concepts were examined in terms of the Piagetian mental schema needed for comprehension. Results show that (1) concept maps and therefore the conceptual structures for a unit on air and/or weather vary widely across texts; (2) all but two conceptual structures are well defined, in that a single concept or group of concepts is not isolated from the total framework; (3) the reasoning needed to comprehend the between-individual concepts is concrete, in that classificational, interactional, and direct observational reasoning are necessary; and (4) these reasoning demands are above the developmental capabilities of a large segment of primary-level children, who function in the preoperational stage. Discussion of the results focuses on the kind of science that is appropriate for primary-level youngsters.