Age Discrimination in Employment

The Age Discrimination in Employment Act of 1967 (ADEA) protects individuals who are 40 years of age or older from employment discrimination based on age. The ADEA's protections apply to both employees and job applicants. Under the ADEA, it is unlawful to discriminate against a person because of his/her age with respect to any term, condition, or privilege of employment -- including, but not limited to, hiring, firing, promotion, layoff, compensation, benefits, job assignments, and training. 

http://www.eeoc.gov/facts/age.html