Dyslexia is a common presenting condition in clinic and educational settings. Unlike the homogenous groups used in randomised trials, educators typically manage children who have multiple developmental problems. Investigations are required into how these complex cases respond to treatment identified as efficacious by controlled trials. This study reports on a sub-lexical intervention in a student with dyslexia and Asperger's Disorder. Substantial and clinically significant gains were obtained on multiple measures of phonological decoding skill and irregular-word reading. The improvements in word-level skills were accompanied by moderate improvements in text-reading accuracy and reading comprehension. Results are discussed in the context of single-case methodology and the implications for practice and future research are discussed. (Contains 2 figures and 2 tables.)