Following his graduation from Harvard Law School, Judge Posner clerked for Justice William J. Brennan, Jr. From 1963 to 1965, he was assistant to Commissioner Philip Elman of the Federal Trade Commission. For the next two years, he was assistant to the solicitor general of the United States. Prior to going to Stanford Law School in 1968 as Associate Professor, Judge Posner served as general counsel of the President's Task Force on Communications Policy. He first came to the University of Chicago Law School in 1969, and was Lee and Brena Freeman Professor of Law prior to his appointment in 1981 as a judge of the U.S. Court of Appeals for the Seventh Circuit. He was the chief judge of the court from 1993 to 2000.
He has taught administrative law, antitrust, economic analysis of law, history of legal thought, conflict of laws, regulated industries, law and literature, the legislative process, family law, primitive law, torts, civil procedure, evidence, health law and economics, law and science, and jurisprudence. He was the founding editor of the Journal of Legal Studies and (with Orley Ashenfelter) the American Law and Economics Review. He is an Honorary Bencher of the Inner Temple and a corresponding fellow of the British Academy, and he was the president of the American Law and Economics Association from 1995 to 1996 and the honorary president of the Bentham Club of University College, London, for 1998.
He has received honorary degrees from leading American and foreign universities, along with a number of awards, including the Thomas Jefferson Memorial Foundation Award in Law from the University of Virginia in 1994, the Marshall-Wythe Medallion from the College of William and Mary in 1998, the 2003 Research Award from the Fellows of the American Bar Foundation, the 2003 John Sherman Award from the U.S. Department of Justice, the Learned Hand Medal for Excellence in Federal Jurisprudence from the Federal bar Council in 2005, the Thomas C. Schelling Award from the John F. Kennedy School of Government at Harvard University in 2005, and the Ronald H. Coase Medal from the American Law and Economics Association in 2010.