Can you require your employees to submit to a medical exam, drug screen, psychological test, or lie detector test? Find out the rules here.

Workplace testing has become increasingly popular, as employers screen their workers in an effort to figure out who would be the best candidate for promotion or who is responsible for a workplace problem. As long as a test is designed to predict a worker's actual ability to do the job (and is relatively non-invasive), it is probably legal. For example, an employer can generally require typing tests for clerical jobs or agility/strength tests for positions requiring certain physical skills.

For example, one California employer asked applicants to take a comprehensive psychological exam -- including agreeing or disagreeing with such statements as "I am very strongly attracted by members of my own sex" or "I believe in the second coming of Christ" -- before considering them for the position of store security guard. The company eventually paid more than $2 million to settle the dispute.

There are few hard and fast rules about whether a particular test is legal -- courts generally decide these issues on a case-by-case basis, looking at all the facts and circumstances. For the most part, employers can stay out of trouble by using simple common sense. An employer who inquires into an employee's sex life or personal beliefs probably crosses the line, while an employer who tests only for necessary job skills is probably on safe ground.