By day they are computer programmers, television reporters, nurses, pipefitters and guides at the National Gallery of Art. In their spare time, they become performers at the Seabrook Little Theatre in Lanham.

One of the few amateur theater groups that has been consistently producing in this area for more than 20 years, Seabrook has a simple formula for survival, according to President Paul Freirich: "We're open to new people, new ideas and we treat them warmly enough that they stay with us. We become a social fabric and have a good time together. A paragon of theater is everyone getting along together with no prima donnas."

The group's first production in 1961 featured "stage-struck people, teachers from Gaywood Elementary School, who wanted to put on a show," Freirich says.

Now the theater puts on four shows a year and has its own share of loyal patrons. The group rehearses, and usually performs, at the Goddard Middle School in Lanham.

Seabrook Little Theatre draws from Prince Frederick to Alexandria, Va., for its active core of 20 members, and relies on another 50 members who participate in productions intermittently. Some of its members have gone on to more professional theater, including Jim Beard, who performs at the Folger Theatre, and several who now perform on the dinner theater circuit.

But most of the performers have no interest in becoming professional; their involvement in the theater is more like a hobby.

"You have to be amateur to perform with us. It's in our bylaws," says Freirich. The group, which is nonprofit, pays no money to performers or crew members.

Rick Thompson, a newspaper editor, is directing his fourth show for the amateur theater. "There are some critical conditions in a show which do take real professional approaches. But we all have varying degrees of ages and talents and are in a show simply because we love theater. I have worked in other groups in Maryland, but this group is more open -- no cliques and no big egos. That's why we always pull in new members. In our current show, several in our cast and crew are working with us for the first time. Some have never before been in a show."

"Where similar groups run aground is when they become closed," Freirich agrees. "If the board of directors makes all the decisions and is resistant to casting outsiders (friends casting friends, for example), it's fatal."

For Freirich the group is a family affair. His son John, 13, is a member and the lighting technician for the current show. His wife Phyllis is the group's secretary.

The theater receives small grants and help in mailing letters, printing of labels and similar services from the Maryland-National Capital Park and Planning Commission. But the members themselves are largely responsible for sustaining the group. Last weekend, for example, a dozen of them braved bitter cold to haul pieces of the set for their current show from Greenbelt to the Publick Playhouse in Cheverly.

Each production costs $500 to $600; a musical costs $2,000 to $3,000, according to members. The theater's money comes from ticket sales, advertisements in programs, donations from patrons and, sometimes, from members' pockets, they say.

The current show, "Tribute" by Bernard Slade, is scheduled for Jan. 15 and 16 at 8 p.m. at the Publick Playhouse, at Landover and Annapolis roads in Cheverly. The show moves to Marlboro Country Club Jan. 29 and 30 in a dinner theater format.