Some pure alexic readers have been shown to activate lexical and semantic knowledge under brief presentation conditions. This ability is not seen when letter-by-letter reading accuracy is high or the reading impairment is very severe. It is also unlikely to occur under normal untimed presentation because the pure alexic will make deliberate use of their letter-by-letter strategy. This paper presents data from a moderately severe letter-by-letter reader, FD, who had visual processing problems affecting reading. He also had other mild aphasic characteristics. FD showed implicit reading abilities under brief presentation conditions, being able to make lexical decisions and semantic categorisations well above chance. FD was given two therapy programmes, the first, whole word therapy to exploit this implicit ability and the second to improve letter-by-letter accuracy and speed. FD showed some improvement in reading ability after both therapy programmes, particularly for words of personal interest to him. His letter naming accuracy and reading of visually similar words were the most resistant to change. A striking effect of therapy was the cessation of FD's letter-by-letter reading and the emergence of some of the characteristics of deep dyslexia. Even when therapy concentrated on letter accuracy, FD did not revert back to his original letter-by-letter reading strategy.The results are discussed with reference to the two theories of pure alexia. Some conclusions are drawn about the need for therapists to examine and exploit all residual reading skills when devising therapeutic programmes. © 2005 Psychology Press Ltd.