This study was designed to replicate and extend an earlier study in which a therapy programme was carried out with two agrammatic aphasic patients with sentence processing impairments suggested to be at the level of mapping thematic roles and grammatical relations (Byng 1988). In the current study one of the therapy procedures implemented in the previous study was repeated with three different people with long-term ‘agrammatism’. The outcome of the therapy resulted in some gains in sentence production and verb retrieval, but these gains varied across the three patients. Whilst some change had taken place for each person, the pattern of results showed that the quality and extent of the change was different in each case. The potential source for these differences is explored and the implications of the study for the necessary development of theories about therapy are discussed.