The clinical effectiveness of a treatment for children with dyslexia was examined, as well as the moderating impact of plausible cognitive and socio-economic factors on treatment success. Results revealed that the treatment group accrued significant greater gains than the control group in reading and spelling skills. The treatment group obtained a level of reading accuracy and spelling that was comparable with the normative mean. Post-treatment levels of reading rate were comparable to the lower bound of the normal range. Treatment effectiveness was robust against individual differences, except for a moderating impact of phonological memory and rapid automatized naming. (Contains 1 note and 6 tables.)