Three months after heart bypass surgery, Beltsville resident W. Haward Hunt, 75, was back on the job as a volunteer at the Howard B. Owens Science Center in Lanham, where, five days a week, he delights in showing students the fascinations of science. His favorite subject: the workings of the heart.

In his spare time, the retired research scientist also volunteers at Greater Laurel Beltsville Hospital, helping sort and distribute blood samples five days a week. "I'm the sort of guy who has to keep busy," he says.

In 1977, after four years in Taiwan, former television repair shop owner Harold Ludwig, 85, settled in Potomac and set about teaching immigrants to understand English. As a volunteer for the Literacy Council of Montgomery County, he has since put in nearly 7,000 hours tutoring 68 adults, all of whom "make the job easy" because they really want to learn, he says.

Hunt and Ludwig will be the stars Sunday at the 10th annual Volunteer Activist Awards Ceremony planned for Washington's Departmental Auditorium. They are grand prize winners and are among six Maryland residents being honored this year for their dedication as volunteers by the Metropolitan Coalition of Voluntary Action Centers.

In all, 20 residents of the metropolitan area are being honored by the coalition to mark National Volunteers Week.

Some are volunteer teachers, while others have worked with handicapped or mentally retarded adults or donated technical services.

Hunt says his work at the county school system's science center "gives me great personal satisfaction." He volunteered there as soon as it opened, in 1978, after he retired from the U.S. Department of Agriculture, and has since put in 9,000 volunteer hours -- more than five work years -- at the science center. He has been a volunteer of one sort or another nearly all his life -- for the Beltsville volunteer rescue squad, the county Red Cross and the Boy Scouts.

"I'd go to pot right quick if I retired," he said.

At the Science Center Hunt works with students of all ages, teaching a variety of subjects. A unit called "The Heart of the Matter," about the heart and the respiratory system, is the one he most enjoys. He supervises one of three stations set up in the laboratory, teaching students how to use an electrocardiogram machine and how to take each other's blood pressure.

He often receives letters from children telling them how much they enjoyed their visit to the science center and his station in particular, he said. The letters "give me a tremendous feeling of accomplishment, which is essential to me," he said.

Harold Ludwig "has been our 'dean' of tutors for a long time," said Marian Shern, a librarian with the Montgomery literacy council.

A native of Boston, Ludwig owned a TV repair shop there for many years, and did not begin teaching until he moved to Taipei, Taiwan, to live with his son after his wife died in 1974.

An acquaintance told him that a class of Taiwanese university students needed a "model" English speaker, Ludwig recalled, and that he should volunteer. When Ludwig protested that he was 74 years old and had never taught in his life, the friend said, "You've got a good gift of gab. You'll be okay."

He soon came to love teaching, and, when he moved to this area, began teaching for the council, visiting two or three students a day, to converse in his thick Boston accent for two hours at a time. "It was like a full-time job for him," said Shern.

Other Maryland winners include:

Jill Katz, 16, who has worked with mentally retarded adults in Montgomery County for two years, and John B. Wilson, who has worked for several years with the Montgomery County government on energy conservation and pesticide projects, saving the county thousands of dollars a year.

Harry Hickerson, 74, of Bowie, who has worked for six years at the Great Oaks Center in Silver Spring, a state-run facility for retarded children and adults, and as a foster grandfather at the Glenn Dale Special Center, will also be honored, as will Virginia St. Clair, who lives in Oxon Hill and works with patients at Greater Southeast Community Hospital in Washington, visiting, and cooking for, those who have just returned from the hospital.