The article begins with a discussion of the common features of drug-testing programmes. Regulations, procedures and methods for the collection of biological specimens, the subsequent handling and analysis of the specimens and the reporting of the interpreted results are all important aspects to be dealt with in testing programmes. Different types of testing are examined. Pre-employment testing is a popular type of screening but a number of other programmes exist, including post-accident, reasonable suspicion, post-treatment, random and voluntary testing programmes. The goals of these programmes range from improvement of employees' health, safety, quality of life in the workplace and productivity to reduction of drug misuse in society at large. Emphasis is placed on the need for scientific evaluation and on examining whether those goals have been achieved. In the absence of such evaluation, drug-testing programmes should be carried out with caution; some modifications of existing programmes are suggested.