The advancement of assistive technology device (ATD) outcomes research requires a substantive taxonomy for ATD outcomes. This article describes the assumptions and principles that should underlie such a taxonomy. It advocates for an approach to classifying outcomes that would promote consistency in how ATDs are distinguished, based on their intended effect on the user. The approach is designed to accommodate the widest variety of ATD applications, reflecting combinations of user population, ATD type, service, and context for use. In essence, the provisional taxonomy proposes that ATD outcomes can be effectively operationalized from three vantages--effectiveness, social significance, and subjective well-being. It emphasizes a distinction between the proximal effect of ATDs and the more distal outcomes associated with their use. Because it promotes consistency in the language used for categorizing outcomes, the taxonomic approach should facilitate the development of ATD-specific causal models. The utility of a taxonomy in ATD outcomes research is discussed.