Early in his career as an internist at a teaching hospital and later in private practice, Dr. Jeff Gold felt he needed to add another dimension to his job to gain satisfaction. While he enjoyed his clinical work, Gold also yearned to be intellectually challenged in the business world. "Most people thought I was kind of strange," he says of his transition 18 years ago to dual careers, geriatrics and medical marketing and advertising.

Today Gold, 51 years old, is the medical director and head of medical affairs at the Rebekah Rehabilitation and Extended Care Center in the Bronx, N.Y., and a senior vice president and medical director for Grey Healthcare Group in Manhattan. Together, these two half-time positions satisfy Gold's desire to work with patients on complex clinical cases and be part of a marketing team that creates advertising for pharmaceutical products.

"I've rounded out my must-have list of criteria for my career," he says. And perhaps just as important, Gold says, he has a higher level of job and financial security. "If one industry suffers a downturn, I am still likely to be employed by the other."

Gold is one of a growing number of professionals who are opting out of the traditional one-job track. Instead, they are crafting a portfolio of careers comprising multiple part-time jobs that, when combined, are equivalent to a full-time position. The number of people pursuing these dual — or tri — track careers has doubled in the past couple of years, says John A. Challenger, president of the outplacement consulting firm Challenger, Gray & Christmas.

The types of people who craft portfolio careers are as diverse across age groups as they are across industries. This alternative approach to work isn't just about cobbling together a patchwork of freelance gigs but rather is a distinct career path that allows people to combine their interests and not be seriously penalized in the process. "You want to try to find a combination of things that work well together like writing, teaching, speaking and consulting," says Marci Alboher, who calls these multipronged careers "slash careers" in her book "One Person/Multiple Careers: A New Model for Work/Life Success." Alboher says she knows successful portfolio careerists who have become both a pilates instructor and an art dealer; an attorney and a minister; a psychotherapist and a violin maker; and a teacher, dancer and puppeteer.