Because workplace drug use poses occupational hazards drug testing has become routine. The reliability of such tests may be affected by the authenticity of the urine sample, the accuracy of the laboratory analysis, and consumption of certain medications or foods. A second test should be given to confirm positive results. Employee assistance programs have been widely accepted as a way to deal wtih drug-using employees. While few companies currently test for AIDS, coworker fears and the enormous medical expenses associated with treatment make increased testing likely in the future. Employee medical screening of all kinds raises issues concerning employers' rights to protect themselves versus employee rights to privacy. Historically, common law has given private-sector employers great discretion in their personnel policies. However, medical screening constitutes a search under the fourth amendment. Consequently, in determining the constitutionality of drug or other testing, a reasonableness standard applies. In general, reasonableness of drug testing has been upheld when reasons have been explained and advance warning of testing has been given. Because a consensus exists that AIDS does not constitute a danger in normal working situations, actions based on test results could result in a successful charge of employment discrimination. 18 references.