It is at least a decade since scientists turned their imaginations to creating new compact, portable test instruments and self-contained test kits that could be used to analyze urine and saliva for alcohol, drugs, and their metabolites. Although the potential applications for such tests at the site of specimen collection, now called "on-site" or "point-of-care" testing, range far beyond hospital emergency rooms and law enforcement needs, it was catalyzed by the requirements of workplace drug testing and other drugs-of-abuse testing programs. These programs are now a minor national industry in the United States and in some western European countries, and cover populations as diverse as the military, incarcerated criminals, people suspected of driving under the influence of alcohol and other drugs, all athletes from college to professional ranks, and of course the general employed population, which is monitored for illegal drug use and numbers in the millions. It is not surprising, then, that the need for rapid and precise tests, conducted economically by trained professionals, has become a major goal. Current government approved and peer reviewed laboratory methods for urine analysis serve present needs very well and have become remarkably robust over the past twenty years, but the logistics of testing some moving populations, such as the military, the Coast Guard, workers on off-shore oil platforms, and athletes-perhaps the most mobile of these groups-are unacceptably cumbersome.