Under the National Labor Relations Act, private employers must negotiate with labor unions to define drug testing procedures to be used on employees. In States that have adopted statutory provisions mandating collective bargaining by public employers and labor organizations, the same obligation pertains to public sector employers. These constitutional challenges to mandatory drug testing are discussed, along with a suggested analytical framework for unions to use when negotiating drug testing procedures with employers. Effective collective bargaining should enable labor and management to ensure counseling and treatment for drug-dependent employees while protecting employees who do not use drugs from unlawful intrusion into their private lives. 10 footnotes.