This study was conducted to assess the effectiveness of the Individualized Reading Evaluation and Diagnosis (iRead) Inventory for accurately assessing specific decoding sub-skill weaknesses and for informing the development of targeted interventions to improve the reading abilities of students. The iRead Inventory is a curriculum-based, specific skills mastery measurement tool for assessing specific decoding weaknesses. Students read word lists targeted to specific vowel combinations to determine weaknesses with particular combinations. The study assessed whether the iRead Inventory could distinguish specific decoding sub-skill weaknesses for students and whether the iRead Inventory was effective in supporting the development of interventions to improve those decoding weaknesses. Students were screened for dysfluency and three students were identified as having primarily decoding issues were selected for the intervention phase of the study. The intervention phase of the study involved using a multiple baseline, randomization design with the three participants receiving interventions beginning at randomly selected times. The iRead Inventory was utilized to identify specific vowel combination difficulties for intervention and the participants were provided direct, sequential instruction targeted to the identified specific decoding weaknesses. The participants’ reading progress was monitored using Reading-CBM (R-CBM) and Nonsense Word Fluency (NWF) measures. In addition, their progress with learning the specific sub-skills was monitored using the iRead Inventory. The iRead Inventory was found to reliably assess specific decoding deficits. Interventions that were developed using the iRead Inventory were shown to improve the decoding abilities of all the participants. The two participants who received interventions earlier showed gains in oral reading skills and mastered a number of specific vowel combination decoding skills. The participant who began interventions last showed less gain in both abilities. In addition, there seemed to be a learning curve phenomenon whereby participants did not exhibit gains associated with the interventions until approximately two and one half weeks after interventions were initiated. Further research can include assessing the reliability of the iRead Inventory, researching its utility for designing interventions for a broader population, and assessing the implications of a potential learning curve phenomenon for making educational decisions.