The purpose of this state report card is to provide the general public and policymakers with information they can use to assess and improve postsecondary education in each state. "Measuring Up 2006" is the fourth in a series of biennial report cards. The report card grades states in six overall performance categories: (1) Preparation: How adequately does the state prepare students for education and training beyond high school?; (2) Participation: Do state residents have sufficient opportunities to enroll in education and training beyond high school?; (3) Affordability: How affordable is higher education for students and their families?; (4) Completion: Do students make progress toward and complete their certificates or degrees in a timely manner?; (5) Benefits: What benefits does the state receive from having a highly educated population?; and (6) Learning: What is known about student learning as a result of education and training beyond high school? Findings for Illinois include: (1) Illinois has improved in preparing high school students to succeed in college. This year Illinois receives a B in preparation; (2) Despite a decline in performance, Illinois continues to do well in enrolling students in higher education when compared with other states. This year Illinois receives an A in participation; (3) Illinois has seen a notable decline in the provision of affordable higher education. This year Illinois receives an F in affordability; (4) Illinois has made substantial gains in the proportion of students earning a certificate or degree in a timely manner. Illinois receives a B+ in completion this year; (5) Illinois has made gains in the benefits the state receives from having a more highly educated population. This year Illinois earns an A in benefits; and (6) Illinois is among nine states that receive a "Plus" in Learning because data were sufficient to compare at least two of the three Learning categories in the state results described in this paper. This report also includes international comparisons, additional information, questions and answers, and state grades. (Contains 2 figures.) [For "Measuring Up, 2006. The National Report Card on Higher Education," see ED493360.]