The legal position regarding workplace drug testing in the UK is assessed. Workplace drug testing in construction appears to be legally defensible provided the procedures meet certain criteria. The various forms of employment-related drug testing programmes are outlined. These include pre-employment testing, random testing, post-accident testing, and post-treatment testing. Previous research on the influence of workplace drug testing on occupational safety is reviewed. Results of a survey to evaluate the extent to which workplace drug testing has been implemented by UK contractors are analysed. Reasons that have led contractors to introduce workplace drug testing include: to promote the safety of their employees; because drug testing is seen as an effective deterrent; and company concerns about their liability for drug-related incidents. The factors that have influenced the decision for some companies not to implement workplace drug testing include: concerns for increased legal liability and employee opposition to drug testing. There is also the belief that drug testing is an invasion of privacy and that it is not effective in reducing occupational accidents. The effectiveness of workplace drug testing in construction remains debatable.