Despite the widespread use of Orton-Gillingham (OG) based approaches to dyslexia remediation, empirical support documenting its effectiveness is lacking. Recently, Chia and Houghton demonstrated the effectiveness of the OG approach for remediation of dyslexia in Singapore. As a conceptual replication and extension of that research, we report results of 39 students with dyslexia aged between six and 14 years enrolled in an OG intervention programme over a period of one year in a single-subject research (pre-test/post-test) design. Analyses of variance showed that students significantly improved in standardised tests of reading and spelling with moderate effect sizes (Cohen's d = 0.52-0.58). Additionally, an inverse relationship was found between students' ages when they began intervention and gains made during the intervention. Results thus indicate the effectiveness of an OG approach in remediating literacy difficulties in students with dyslexia and, taken together with previous studies, further suggest the importance of early identification and intervention.