Scientific texts commonly present principles by first giving a proof and only afterward stating the principle—a “proof-first” organization. This specialized text structure differs from conventional structures in that it lacks thematic information to guide text processing. The current research examined the effects on comprehension of this proof-first organization. This was done by comparing the processing of proof-first texts to that of “principle-first” texts, in which the theme (i.e., the principle) is stated at the beginning. Readers had more difficulty determining what was important when reading proof-first texts and reorganized proof-first texts into a principle-first structure when summarizing. The proof-first organization also decreased recall of the principle. These results suggest that, compared with a principle-first structure, the proof-first structure increases processing difficulty and results in a less complete text representation.