To consider pertinent issues towards developing a coherent theory of the auditory processing disorder (APD). By identifying the conceptual and methodological shortcomings that have thwarted development in this area for decades, we propose solutions to achieve a veridical endpoint to advance the field. Concerted efforts in the theoretical, experimental, and clinical domains have focused on validating the APD by demonstrating the " modality specificity " of the deficit. The importance of this conceptual framework is the delineation of auditory-perceptual dysfunctions from more generalized " supra modal" deficits, like those related to attention, memory, and language. Because contemporary schemata have limited the assessment of APD to auditory tasks alone ( unimodal testing), functional dissociations cannot be established, indeterminate diagnoses are problematic, and progress remains unduly constrained. The use of matched tasks in multiple sensory modalities is advocated as a diagnostic imperative to remedy this deficiency. Themes covered by this review include the need to develop a coherent theory of APD, to identify and limit factors which confound a valid diagnosis, and to validate the diagnosis by demonstrating the " modality specificity " of the deficit. Without an obligatory theoretical designation, the APD will remain as an obscure and controversial entity, limited to indeterminate test results and misdiagnoses.