IF YOU -- or your child -- just can't seem to forget the gymnasts who brought home the gold for the United States Olympic team last summer, head out to Montgomery College on Saturday or Sunday to watch some of the nation's fuure stars compete for the Eighth Annual Nation's Capital Cup. The meet, sponsored by the MarVaTeens gymnastics team of Rockville, opens the national December-to-May season for competitive gymnasts, and is considered a proving ground for future champions. Four years ago, a sprite named Mary Lou Retton took home individual honors.

More than 150 young women from 50 clubs in 16 states -- plus Canada and Puerto Rico -- will face off in senior-level preliminary competition Saturday at 9 a.m. and 1 and 5:30 p.m. In addition, a hundred of the best junior-level gymnasts -- rising stars who haven't yet met the 8.5 judging-ratings minimum for senior-level participation -- will compete Sunday morning. The top 10 individual athletes in each senior-level event will continue to the finals at 2:30 p.m. Sunday.

The Capital Cup is "a testing ground" for the best clubs' best gymnasts, because it's the first time each season that the stars square off against one another, says Gary Anderson, MarVaTeens owner and coach. "The clubs' coaches are like a fraternity," he adds. "They all know each other and want to see who's coming up."

Teams entered in the meet are seeded -- the best will compete at 5:30 Saturday, for example. But Anderson points out that outstanding individual gymnasts may appear at other times. Jenny Rhee, 17, who is the Capital Cup defending champion, and Pan-American team member Lisa Whittwer, 16, of Houston, will compete at 1 p.m. because their teams, the Prince George's Gymnastics Club and Texas Academy, are seeded for that time slot.

MarVaTeens, which won the cup in 1982, will compete at 5:30 against the 1983 defending champions, the Allentown (Pa.) Parkettes, and other top-flight clubs. Two MarVaTeen gymnasts, Nadia Mason and Christie Lynch, both only 11, will compete at the senior level along with 17 other girls from the Washington area. Twelve other local girls are scheduled to participate in the junior division.

Besides MarVaTeens and Prince George's Gymnastics, other local clubs in the meet include Docksiders from Annapolis, Karons of Fairfax, Pete's of Springfield, Saints of Waldorf, Springettes of Gaithersburg, Royal Ts of Bowie and Gymini of Herndon.

While you marvel at the strength and skill of these youngsters, your own child may be watching and burning with envy. Tell your aspiring athlete most of these heroines began the long climb to mastery years ago through private lessons.

Remind yourself, too, that creating a young gymnast may mean dedication on your part: years of tuition and meet entry fees, of carpooling and chauffeuring to lessons, of driving to out-of-town meets and spending hours waiting for the few seconds when your child performs; of car washes and bake sales and other money-making endeavors so that the club's gymnasts can go to distant meets. MarVaTeens' team travel fund -- which sent young women to Canada, Moscow and Israel last year -- gets a big boost from proceeds from this weekend's meet.

One "gymnastics mother" -- Mary Silverman -- quit her job to help shepherd her only child through a gymnastics career. Susie Silverman, now 13 and a student at Georgetown Day School (which does not have a gymnastics team), began taking lessons at the age of seven from MarVaTots & Teens. Susie's one 45-minute lesson a week expanded to twice weekly, then three times and now five days a week. Last year, she participated in meets in California, Arizona and Alberta.

To accommodate her daughter's rising career, Mary Silverman gave up teaching third-year medical students and nurse- practitioners at Catholic University and George Washington University medical school, and took a 70 percent pay cut to work at the club as an assistant to Anderson. Even when she decided to take the job, she says, her "primary consideration was whether I was going to be interfering with the coaching" of her daughter.

Silverman acknowledges that fashioning her career around her daughter's training has "become a huge kind of involvement." But she adds, "It's upbeat . . . sort of a labor of love."

A gymnastics parent would understand.

GETTING TO THE CAPITAL CUP -- From the Capital Beltway, take I-270 North. Exit at Route 28 (Rockville exit). Turn left on West Montgomery Street, continue two blocks to Mannakee Street and drive one mile to Montgomery College on the left. Tickets: Children pay $3 and adults $4 for all-day Saturday (sessions 9 a.m., 1 and 5:30 p.m.); children pay $1.50 and adults $3 for the Sunday-morning juniors-only session at 9 a.m.; both adults and children pay $5 for the senior finals at 2:30 Sunday. For information, call 424-8545. GETTING INVOLVED

MarVaTots & Teens, with 1,400 students the largest club in the metro area, is at 5636 Randolph Road, Rockville. 424- 8545. The club enrolls tots as young as 2 in classes with their parents. Prospective students may try out a single class for between $6 and $12, depending on ability.

Here's a sampling of other area clubs and where to find them:

DOCKSIDERS -- 726 Second Street, Annapolis. 301/262-2718.

GYMINI GYMNASTICS CLUB -- 310 Victory Drive, Herndon. 471-6088.

KARONS GYMNASTICS CENTER -- 3731 Pickett Rd., Fairfax. 323-0088.

PETE'S GYMNASTICS CENTER -- 6700 Industrial Rd., Springfield. 256-2435.

PRINCE GEORGE'S GYMNASTICS CLUB -- 5018 Herzel Place, Beltsville. 937-7584.

ROYAL-Ts -- 2125 Baldwin Avenue, Crofton. 721-1116.

SAINTS GYMNASTICS CLUB -- 109 Post Office Road, Waldorf. 843-3322.

SPECS GYMNASTICS CLUB OF HERNDON -- 124 Spring Hill Rd., McLean. 893-7420.

SPRINGETTES -- 9108 Gaither Road, Gaithersburg. 948-3006.