The diagnostic problem of how validly to assess the language of children who speak dialects different from Mainstream American English (MAE) has challenged the field of communication disorders for several decades. The key to its solution is to recognize differences due to dialect or development and remove them from the initial diagnosis of a disorder. A new approach to the puzzle, implemented jointly by University of Massachusetts scholars and the Psychological Corporation (TPC), takes two directions: (1) it provides new normative data on African American English (AAE) development, and (2) it proposes a level of analysis deeper than dialect for the discovery of alternate markers of a disorder. We present three objectives for a language assessment instrument designed to solve this longstanding problem: (1) to answer the problem/no problem question for a given child; (2) to provide explanatory data about the nature of the problem; and (3) to achieve objectives 1 and 2 in a way that is culturally and linguistically fair to both speakers of MAE and speakers of other dialects of English such as AAE.