BACKGROUND: The significance of imageability and concreteness as factors for lexical tasks in aphasic individuals is under debate. No previous treatment studies have looked specifically at training abstract words compared to concrete for improved lexical retrieval in patients with chronic aphasia. AIMS: The goal of the present study was to determine the efficacy of a treatment for lexical retrieval that is based on models of lexical processing by utilising abstractness as a mode of complexity. It was hypothesised that training abstract words in a category will result in improvement of those words and generalisation to untrained target concrete words in the same category. However, training concrete words in a category will result in the retrieval of trained concrete words, but not generalisation to target abstract words. METHODS and PROCEDURES: A single-participant experimental design across participants and behaviours was used to examine treatment and generalisation. Generative naming for three categories (church, hospital, courthouse) was tested during baseline and treatment. Each treatment session was carried out in five steps: (1) category sorting, (2) feature selection, (3) yes/no feature questions, (4) word recall, and (5) free generative naming. OUTCOMES and RESULTS: Although participant 1 demonstrated neither significant learning nor generalisation during abstract or concrete word training, participants 2, 3, and 4 showed significant learning during abstract word training and generalisation to untrained concrete words. Participants 3 and 4 were also trained on concrete words, on which they improved, but did not show generalisation to untrained abstract words. CONCLUSIONS: The results of the present experiment support our hypothesis that training abstract words would result in greater learning and generalisation to untrained concrete words. They also tentatively support the idea that generalisation is facilitated by treatment focusing on more complex constructions (Kiran and Thompson, 2003; Thompson, Shapiro, Kiran, and Sobecks, 2003).