An out-of-work Lehman Brothers broker, a laid-off Ford autoworker, and a broke A.I.G. executive walk into a bar…and they probably don't want to hear a joke.

There's not much to laugh about in these tough economic times, with companies failing and jobs vanishing. But humor consultants, citing decades of research, say levity is exactly what's necessary. Encouraging employees to have fun can boost morale, foster creativity, reduce absenteeism, and increase profits.

"Companies where humor is part of the culture have a competitive advantage," says John Morreall, a humor consultant in Williamsburg, Virginia, whose clients include Corning, I.B.M., and Cargill.

A classic example is Southwest Airlines, whose zany founder Herb Kelleher is known for wearing Easter-bunny suits and jumping out of overhead bins. Flight attendants often break into song, and the corporate headquarters has a volleyball court.

"They've done well, even when other airlines are struggling," says Morreall, who is also a religion professor at the College of William and Mary.

But is it possible to teach lightheartedness, especially when things seem as dire as they seem today? Can companies mandate fun? Humor is subjective, after all; what cracks up Ed in engineering won't necessarily amuse Mary in marketing.

"It's not about teaching people how to tell jokes or be wacky," says Edward Dunkelblau, a humor consultant in Northbrook, Illinois, whose clients include United Airlines, Allstate, and Accenture. "It's about teaching them to be playful and find enjoyment in their jobs—no matter how difficult the times may be."

Dunkelblau, a clinical psychologist, says he tells "humor impaired" executives who seek his counsel that something as simple as keeping a Slinky on their desk can make them more approachable and send a signal to employees that it's okay to have fun at work. "They are amazed at how many people pick these things up and play with them," he says.

He also encourages overly serious managers to keep humor journals of things they find amusing and to share those things with others: "The idea is that they don't have to be funny, but they have to recognize what is funny."

Humor consultants say corporate clients typically call on them during stressful times—following layoffs, amid a buyout, or perhaps after the introduction of a new computer system. Fees range from $500 for a speech to $50,000 for several months of assessment and intervention.

Playwood Systems, a family-owned playground-equipment maker in Lewisburg, Pennsylvania, hired a humor consultant last year simply because it wanted its culture to reflect its product. "You could walk around the building and it was so serious; you'd have no idea what we did," says Kevin Cook, Playwood's director of sales and marketing.