To evaluate the effects of an intensive tertiary reading intervention, 27 students with severe reading difficulties and disabilities, 14 of whom had demonstrated an inadequate response to 1-2 tiers of prior reading instruction, received a 16-week intervention package involving decoding and fluency skills. The decoding intervention was provided for 2 hours per day for 8 weeks and was based on the Phono-Graphix program. The fluency intervention followed the decoding intervention and involved 1 hour of daily instruction for 8 weeks based on the Read Naturally program. The 16-week intervention resulted in significant improvement in reading decoding, fluency, and comprehension. Although individual responses to the intervention were variable, 12 of the 27 students showed a significant response to these interventions. Students who had participated in previous Tier 1 plus Tier 2 interventions but remained impaired had a stronger response to intervention in the current study than students who had previously participated only in Tier 1 intervention and students who had not received prior intervention outside of special education.