Teachers play an important role in making decisions about students' accommodations for instruction and assessment. Although teachers are a significant part of the decision-making process, "gaps" in teachers' accommodations knowledge are well documented. Some of these gaps may be due to challenges in providing teacher professional development, including teachers' limited time. A possible solution is to provide online professional development for teachers. Online training has the potential to avoid some of the pitfalls of traditional professional development, which require participants to meet at the same place and time. Because teachers are likely to have Internet access at work and at home, there is greater flexibility in how the training is provided when it is online. The National Center on Educational Outcomes (NCEO) is developing online training for the state of Alabama. In preparation for this development, the authors conducted a review of the literature to learn more about the characteristics of high-quality online accommodations training. This report summarizes the research literature for both professional development on accommodations decision making, and traditional and high-quality online teacher professional development. [This report was funded with partial support from the Multi-state GSEG Toward a Defensible AA-MAS.]