All students, including students with disabilities, must be included in state accountability systems as required by law. In April 2007, federal regulations provided states the flexibility to offer another assessment option--an Alternate Assessment based on Modified Achievement Standards (AA-MAS) for some students with disabilities. The AA-MAS is an optional assessment. The National Center on Educational Outcomes (NCEO) has annually compiled, analyzed, and summarized states' participation guidelines for the AA-MAS since 2007. The purpose of this report is to update information in previous reports. As of October 2009, 14 states (Arizona, California, Connecticut, Indiana, Kansas, Louisiana, Maryland, Michigan, North Carolina, North Dakota, Ohio, Oklahoma, Tennessee, and Texas) had publicly available participation guidelines for an assessment they considered to be an AA-MAS. As of November 2009 only one state--Texas--had successfully completed the U.S. Department of Education's peer review process that determines whether the assessment fulfills the necessary requirements for the state to receive federal funds. Results from this study suggest that states are continuing to develop or update their participation guidelines. A majority of states included flowcharts, decision trees, or checklists in addition to text-based description of guidelines. Over half of the states in the current study required that parent notification and implications for graduation be considered as part of the decision-making process. The participation guidelines differed across states, but all states required that the student must have a current IEP. Additionally over two-thirds of states included the following criteria: consideration of previous performance on multiple measures, learning grade-level content, and not progressing at rate expected to reach grade level proficiency within school year covered by IEP. Appendices include: (1) Participation Guidelines Characteristics by State; (2) State Documents Used in Analysis; and (3) 2009 Participation Guidelines. (Contains 4 figures.)