Locum tenens physician Debra Celec, MD, values the freedom from private-practice headaches.

"I was a bit burned-out from medicine," says Yeaton, who has completed more than 100 assignments in 14 years. "Locum work gives me the light at the end of the tunnel, so I don't get burned-out."

Yeaton's career has taken him to some of the most remote locations in the world and, domestically, to a few slightly less glamorous assignments—from prison and military work to Indian Health Service gigs.

"The common theme across the board is, working as locum tenens offers physicians the freedom and flexibility so they can choose where, when, and how they want to work," Heffernan says. "There is no typical locum tenens physician," though most share a love of travel and curiosity about other cultures.

Heffernan helps physicians seeking assignments, as well as practices in need of their services—and both are increasingly in demand.

Today's physician shortage has helped make locum tenens a $1.9 billion industry, with more than 100 recruiting firms across the country, according to the National Association of Locum Tenens Organizations. The group estimates there are 43,000 locum tenens physicians in America, up from 26,750 in 2001. Of those, 30 percent practice exclusively as locums and 41.5 percent are in primary care.

According to Heffernan, these figures likely will continue to spike as more physicians retire.

Locums are in greatest demand in rural areas and other places underserved by full-time physicians; one staffing firm, Locum Tenens Healthcare, reports that 60 percent of its business is in rural America. Hospitals, too, use locums across a variety of specialties.

Locum life appeals to young physicians because it affords them an opportunity to try out different types of practices and regions before making long-term career choices. Retired physicians extend their careers by taking on locum tenens positions that allow them to work free of the responsibilities of private practice. Staff Care, a physician hiring firm, reports that 92 percent of locums previously held permanent positions—most for more than 20 years.

Women make up a growing percentage of locums, largely because it offers those who are raising families the chance to strike a balance between work and home life. For this reason, female locums are more likely to seek assignments close to home and mostly on a part-time basis. It offers a good way for those who have been out of medicine for a while to dip their toes back into the water.

Hiring locum tenens can be expensive, but many practices are willing to pay to maintain their patient bases (see sidebar, above).

"If you have a physician that is going to be out for any length of time, you run the risk of losing revenue if you don't have another physician available to see those patients," Heffernan says.