SummaryThe differentiation of aphasic articulatory defect and aphasic phonological defect is described. Six non‐fluent and five fluent subjects, from a group of 48 aphasics, were distinguished by their responses in single word tests designed to assess phonemic accuracy and auditory discrimination ability. Discriminant analysis, operating on a subset of the differentiating variables, linked 23 further subjects with the non‐fluent and five further subjects with the fluent group. The response patterns of the enlarged groups were essentially similar to those of the small non‐fluent and fluent groups in variables excluded from the analysis. A speech production problem, characterized by, for example, non‐speech rehearsals, distorted speech sounds and a consistent order of difficulty of phoneme classes associated with consonant complexity, is contrasted with a linguistic disorder in which no consonant class is more problematical than others, phonemic and lexical errors exist in input as well as in output and much stuttering behaviour occurs. The application of appropriate treatment procedures is con