PURPOSE: Kiran and colleagues (Kiran, 2007, 2008; Kiran & Johnson, 2008; Kiran & Thompson, 2003) previously suggested that training atypical examples within a semantic category is a more efficient treatment approach to facilitating generalization within the category than training typical examples. In the present study, the authors extended previous work examining the notion of semantic complexity within goal-derived (ad hoc) categories in individuals with aphasia. Methods Six individuals with fluent aphasia (age range = 39-84 years) and varying degrees of naming deficits and semantic impairments were involved. Thirty typical and atypical items, each from 2 categories, were selected after an extensive stimulus norming task. Generative naming for the 2 categories was tested during baseline and treatment. RESULTS: As predicted, training atypical examples in the category resulted in generalization to untrained typical examples in 5 of 5 patient-treatment conditions. In contrast, training typical examples (which was examined in 3 conditions) produced mixed results. One patient showed generalization to untrained atypical examples, whereas 2 patients did not show generalization to untrained atypical examples. CONCLUSION: Results of the present study supplement existing data on the effect of a semantically based treatment for lexical retrieval by manipulating the typicality of category examples.