Thousands of area youngsters will begin competitive summer swimming this weekend at pools throughout the metropolitan area.

For seven years, the Overlee pool has dominated Division I competition in the Northern Virginia Swim League. As the league's 32nd season draws near, Overlee again is the focus of attention.

"The question is, 'Can someone dethrone them?' " said league president Ray Kostesky.

Last summer, Cardinal Hills and Vienna Woods came closest to ending the reign of the Arlington team. Beginning June 27 and continuing every Saturday through Aug. 1, Overlee's opponents will take their best shots.

This year, the league has grown by three teams to a total of 98 pools competing in 17 divisions. As one of the biggest swim leagues in the country, NVSL has almost 10,000 participants, ranging in age from 8 and under to 18, and is run entirely by volunteers.

Orange Hunt is the Division II favorite, with its toughest meets expected to be against Lakeview Swim Club of Fairfax and Arlington's Tuckahoe, one of the original eight teams in the league. Division III was dominated last summer by Fairfax Station, only in its third season in the league.

Despite some insurance difficulties, NVSL will continue its diving program. The league's 40 teams will compete in five dual meets from June 23 through July 21.

Teams from area country clubs participate in their own swim leagues. The Dominion League, which consists of nine teams in Northern Virginia, will hold its meets each Saturday, beginning this weekend, and will finish up with the league all-star meet Aug. 1-2. Springfield has been the team to beat the last few years. Other top teams in the 18-year-old league include International, Mount Vernon, Evergreen and Westwood.

The Reston Swim Team Association, consisting of eight teams, competes on Monday and Tuesday evenings from June 22 through July 21, and every other Saturday from June 27 until Aug. 1, with the all-star meet topping off the season. The 1,000-member league recently christened Reston's first Olympic-size pool -- at Lake Newport Swim Center -- with a relay carnival.

Most Maryland swim leagues will open their summer seasons Saturday.

The Montgomery County Swim League (MCSL), one of the oldest and biggest in the area, has a six-week regular season. More than 4,000 youngsters compete for 77 teams, which are divided into divisions of six teams each (one division has five teams). Teams in each division are paired on a rotating basis each weekend.

Teams are ranked based on a cumulative time-in-the-water standard based on the previous season's performances.

In the first week, the second and fifth teams meet, the fourth and third teams and the sixth and first. The pattern continues until the final week, when the first- and second-ranked teams compete, usually for the division title.

There are 46 events in a regular season meet divided among five age groups, 8 and under, 9-10, 11-12, 13-14, 15-18.

The divisional championship meet is scheduled for the Saturday following the final regular-season meet. A team's top two swimmers in each event are entered in a championship-style competition in each division.

After the divisional championships, the top 16 youngsters in each event will compete in an all-star meet Aug. 2 at the Rockville Municipal Swim Center. No teams scores are kept in this meet as the emphasis is on individual performances.

Midway through the season, the leading 16 individuals have the opportunity to compete in an event in which they swim double the distance of their regular event in the Rockville Municipal long-course (50-meter) pool. This year's long-course meet will be held July 14.

The other leagues are structured along much the same lines. The four divisions of the Country Club Swimming and Diving League will hold meets Tuesday and Thursday evenings beginning June 25 and ending July 16. The meets are unique in that, unlike in the MCSL, where every pool is a standard length of 25 meters, in the CCSDL, lengths vary.

Divisional relay carnivals will be July 7 and divisional championships July 21 at designated pools. The league championships will be held at the Kenwood pool, which is 100 feet long, July 27, 28 and 29.

The Prince-Mont Swim League has eight divisions of six teams each, also broken up according to ability. The first regular-season meet will be Saturday and the dual-meet season will end July 18. The divisional championships will be the following Saturday and the all-star meet will be at Cheverly Aug. 1.

The D.C. Department of Recreation's Competitive Swim League, consisting of East, South and West divisions, will start up next week, with six teams in each division.

The team designated as the home team for the week in each division will compete twice during the week: Monday and Thursday for East Division teams, Wednesday and Friday for South Division teams and Saturday and Tuesday for West Division teams.

The regular season will run through July 11, with the division relay championships scheduled for July 18. Langdon Park hosts the East Division championships on Monday, July 20; Oxon Run will be the site of the South Division championships on Wednesday, July 22. The West Division championships will be Tuesday, July 21, at Banneker.

City championships will be Saturday, Aug. 1, at Capitol East.