An application of the fourth amendment's balancing test of reasonableness for determining whether governmental interests outweigh individual privacy interests suggest five situations in which urinalysis drug testing would be justified. These include applicant screening, tests of trainees and probationary officers to determine if they can fulfill their duties, regularly scheduled physical examinations, in connection with a change in assignment, and as a result of certain observed behaviors or actions. While unannounced, random testing may be most effective in detecting and deterring drug use among law enforcement officers. In the three cases in which unannounced random tests were challenged, the courts found the policies unconstitutional as drafted. A number of features can be incorporated into random test programs to increase their chance of withstanding constitutional challenges: the program should clearly state that it is applicable to all officers, the selection process must be truly random, the need for such testing should be established, and a limit should be set on the number of times any individual can be tested over a given period. 24 references.