New technologies and practices, such as drug testing, genetic testing, and electronic surveillance infringe upon the privacy of workers on workplaces. We argue that employees have a prima facie right to privacy, but this right can be overridden by competing moral principles that follow, explicitly or implicitly, from the contract of employment. We propose a set of criteria for when intrusions into an employee''s privacy are justified. Three types of justification are specified, namely those that refer to the employer''s interests, (...) to the interests of the employee her- or himself, and to the interests of third parties such as customers and fellow workers. For each of these three types, sub-criteria are proposed that can be used to determine whether a particular infringement into an employee''s privacy is morally justified or not. (shrink)