This Note describes the development and testing of CLARIFY, a computerized writing aid designed to assist writers in revising technical prose. CLARIFY is not a traditional readability formula; its design reflects research on how English speakers understand sentences. CLARIFY flags sentences that have certain patterns of nominalizations, prepositional phrases, and forms of the verb to be. The choice of these features reflects research which suggests that the dominant strategy employed by English speakers in interpreting sentences is to assume a subject-verb-object (SVO) structure. The features that CLARIFY flags are good surrogate indicators that a sentence does not have an SVO structure, and therefore, that the initial interpretive strategy will be unsuccesssful. In developing CLARIFY, the authors tested various patterns of these features, and obtained user comments about the system's usefulness and effectiveness. Like all computerized writing aids, CLARIFY has limitations, which are discussed in the Note. CLARIFY is in general use at RAND, where it is also continuing to be tested.