The Age Discrimination in Employment Act of 1976 (ADEA) made it unlawful to discriminate against employees or applicants who are between 40 and 65 years of age. Subsequent amendments eliminated the age cap, effectively ending most mandatory retirement at age 65. Most states and local agencies, when acting in the role of employer must also adhere to provisions of the act that protect workers from age discrimination. You can’t get around the ADEA by replacing employees over 40 years of age with those who are also over 40. In O’Connor v. Consolidated Coin Caterers Corp, the U.S. Supreme Court held that an employee who is over 40 years of age might sue for discrimination if a “significantly younger” employee replaces him or her, even if the replacement is also over 40. The Court didn’t specify what “significantly younger” meant, but O’Connor had been replaced by someone 16 years younger.