Recent research has suggested that the professional development general educators receive is not adequately preparing them to properly implement inclusion-based practices. In this study, data from the Study of Personnel Needs in Special Education was used to investigate the relationship among teachers' years of experience teaching students with Individualized Education Programs (IEPs), the amount of professional development received over the past 3 years, and teachers' self-perceived ability to adapt instruction for students with IEPs. Results indicate that any amount of professional development in a 3-year period significantly predicts teachers' perceived ability to adapt instruction; however, at least 8 hours of professional development in a 3-year time frame was related to an increase in teachers' perceived ability to adapt instruction, more than twice the effect of less than 8 hours. Additionally, professional development was found to be a better predictor for increasing perceived ability to adapt instruction than was teacher experience with instructing students who have IEPs. (Contains 3 tables.)