As a Marine working on his doctorate in education, Rick Crain for years drove his Toyota truck twice a week from Quantico to Charlottesville, stayed overnight and set out at 4 a.m. to get back to the base the next day.

That experience helps him understand the needs and demands of his students at Strayer University, almost all of them working adults who come to him for three-hour classes after a full workday or on the precious weekend.

"I've been there," said Crain, 60, a professor of business administration and general studies, and business administration department head at Strayer's Fredericksburg campus.

Continuing education and training for working adults is a growing field, both to keep employees current with the latest technology and to help them advance as managers and executives. A growing emphasis by businesses on certification in computer information systems and business management is also driving the demand.

With Strayer's student population rising by 28 percent in two years to 10,449 last fall, and with more than a dozen Washington area campuses and workplace locations, the university is looking for professors who can teach its business-oriented courses, especially computer information specialists.

Those interested in this career need to be prepared for older, well-motivated and demanding students as well as the lengthy night and weekend classes geared to them. About half of Strayer's faculty is full time, earning an average of $53,000 when carrying a full load; half are adjunct, paid by the class. The average age of Strayer's students is 33, and 70 percent attend classes in the evening.

"They expect a great deal of the instructors," said Crain. "They are wearing so many different hats, that's what makes these students fun."

Crain earned a BA in history from Duke University, but soon found himself drafted and heading to Vietnam, where he served two tours as a Marine. He spent 29 years in the Marines before retiring in 1990 and working for a while as a fund-raiser for a nonprofit organization. Then in 1992, a friend of his at Strayer's Manassas campus suggested he might like teaching at the new facility opening up in Fredericksburg, near his home.

"I always wanted to be a teacher. ... I was just looking for the right opportunity," said Crain, who had earned his master's in education in 1974 and his doctorate in 1982, both from the University of Virginia. The practical nature of teaching working adults suited him, too. "At Strayer they're teaching relevant programs of instruction, and it was a perfect match for me."

It means having to keep up to the minute on business trends and needs. "We no sooner get the ink dry on our catalogue than they will add a course, because that's what the workplace wants," Crain said. It also means engaging and satisfying the students, who evaluate their professors at the end of each 11-week quarter and whose views are given great weight in terms of who stays and who goes.

This keeps professors on their toes -- "frosty," as Crain calls it -- but could also be nerve-racking to anyone who relies on this job as the sole family income (unlike Crain, who has his military retirement).

"You can't hide behind tenure [at Strayer]. You're as good as the last group that appraised you," said Crain.

ON THE JOB: Continuing education instructor

Salary: $53,000 for full-time professor carrying full load for four quarters

Skills/education required: Master's degree or doctorate in field teaching (in the computer information field, at least a BS or BA)

Experience necessary: Some teaching preferredOn the Job

Radiology technologist

Salary: Low $30,000s

Skills/education: Two-year certification degree

Experience: Time in a health-care setting is a bonus, but good basic technical skills are a must.