When Bill Sandusky of Olney arrives at Watkins Regional Park he is still dressed in the uniform of a government bureaucrat, subset Census Bureau. But, disappearing into the men's lavatory, he sheds shirt, tie and shiny shoes and emerges moments later as SOFTBALL MAN.

Softball Man -- fielding hot grounders with a stab of the hand. Softball Man -- smashing vicious line drives with a flick of the wrists. Softball Man -- wearing those peculiar beltless shorts that accentuate what most pants seek to obscure.

In the hour after work ends, transformations like the one that Sandusky undergoes occur in office restrooms, private homes, even discreetly parked vans as insurance agents, letter carriers, heavy-machine operators -- people who are otherwise quite reputable -- prepare to occupy all the flat green space in greater Washington.

There are roughly 6,200 adult softball teams and an estimated 85,000 players in the metropolitan area. And that's just counting the ones that play on city and county-run fields. There are fast-pitch leagues and slow-pitch leagues. Men's leagues, women's leagues and fast-growing coed leagues. There are tavern teams, office teams, church teams and industrial teams.

So many teams in the District (about 950) and Alexandria (160) that an unofficial freeze has been instituted. So many teams that Braddock Park, a six-field facility in Fairfax County, hosts 18 games each weeknight and 72 games each Saturday and Sunday.

The game has become so popular that "you can't find a place to practice before the season starts. Every open space I know of has somebody out there hitting balls on it," says Charles Dukes, whose commercial real estate firm sponsors two teams in Prince George's County.

Softball buffs trace the boom in the game's popularity to the fitness movement of the early '70s. "There is a lot more tennis than there used to be, a lot more soccer, so it certainly profited from people looking for an active, outdoor thing to do," says Dukes, former chairman of the Maryland-National Capital Park and Planning Commission who is a member of the Washington Metropolitan Softball Hall of Fame.

It also profited from being alarmingly easy to play.

"You got a nice big ball," Bill Sandusky says. "It comes up real slow and if you can hit it, you can play."

"And because the ball is almost always hit, everybody is in play all the time," Dukes adds.

In other sports (except golf and bowling, which are primarily occasions for sartorial transgressions), poor physical condition or a paucity of athletic skill can handicap the prospective player. Not so in softball. Most local jurisdictions offer competition at a variety of levels so it isn't hard to find a game that moves at the appropriate pace.

As for advanced age, Russ Reber, tournament chairman for senior softball (50 years old and over) in Northern Virginia, reports that his league boasts an octogenarian with artificial knees. "Our motto is 'You don't stop playing because you grow old, you grow old because you stop playing,' " Reber says.

But the fact that the game is accessible doesn't really explain why it engenders such passion in its participants. To wit:

Mark Maners, a 24-year-old pharmacist from Alexandria, drives the length of Braddock Road, from the Beltway to Clifton, each Tuesday at the height of rush hour to play for Bradley and Lowe Travel Inc.

Vic Knott, a director of personnel for the Department of the Army, umpires five nights a week and plays the other two.

Kathy Courtney-Hochul, a lobbyist who lives in Cleveland Park, says she enticed her then-fiance, Bill, a lawyer, to leave Buffalo and join her in Washington by securing him a spot on one of Prince George's County's better softball teams. This arrangement facilitated their marriage.

Sharon Sealock of Fairfax, a member of the Washington Metropolitan Softball Hall of Fame, planned the births of both her children so they would not interfere with the season. "The second one was close," she says. "He was born in early April, but I was on the field 4 1/2 weeks later."

Some of the more serious players are driven to this extreme by a lust for competition and perhaps the sense that playing a childhood game helps them hold on to a piece of their past. "These guys are as competitive as they ever were," Tom Huston says of his teammates, who are in their late twenties and early thirties. Huston plays for Sports Spot, a team sponsored by a Sterling-based sportswear store. "They are a little bit slower, a little bit heavier, a little bit older, but they are still competitive," he says.

These are the type of players for whom devotion begets the need to accessorize. Take, as an only slightly unusual instance, the dark-haired young man who arrived early for his game at Braddock Park several weeks ago. He was one of those guys who seem to have a limited supply of utterances and so guard them zealously. "Doin'?" he would say when approached by an acquaintance.

The young man was carrying his own personal bat sack, a long, brightly colored nylon pouch that holds his personal bat, along with glove and other equipment. He was already wearing (a) a team jersey, (b) Lycra leggings of the sort favored by Michael Jordan and bicycle messengers, (c) gym shorts, (d) a wristband, (e) a cap, (f) two pairs of sweat socks and (g) Nike cross-training sneakers.

One might have supposed he was prepared to play, but one would have been wrong. Ultimate readiness was not achieved until he slipped on (h) another jersey and (i) a pair of uniform pants, and shed one pair of socks and his Nikes for (j) stirrup socks that matched his jersey, and (k) red rubber-cleated shoes.

At times like this it is worth remembering that sometime in the middle of this century, inner-city kids played stick ball on the street in front of their homes because all the game required was a broom handle and a Spaldeen. But it is also worth remembering that one of softball's seductive charms is the opportunity to act, however briefly, as though one were a professional athlete.

In men's league competition this leads to a lot of spitting. It leads to a proliferation of batting gloves and an inexplicable fondness for reinforced polyester shorts generally associated with gym teachers. It leads to brick masons, claims adjusters and college professors developing the tight-muscled swagger of high school jocks and then discarding it the moment they head for home. All of this makes the men's game somewhat embarrassing for outsiders to watch.

"Didn't you ever read that book Women Who Leave Men Who Play Softball?" asked a woman at Watkins Regional Park in Largo one recent evening as she wheeled a stroller behind the third-base bleachers.

Not everyone who is devoted to softball, however, is burdened with the desire to act out their Jose Canseco fantasies. Others are attracted by more low-key charms.

"I don't know of a better way to relieve stress and work out tension than playing softball," says Greg Phipps, park manager at Braddock Park.

"This is not really that easy an area to meet people," says Martha Lorenz, who works at the National Captioning Institute and plays in a coed league and a women's league in Fairfax County. "Everybody goes to work and then they all shoot off in different directions. When you are out there playing, you obviously have something in common.

"My two best friends in this area are people I met through playing softball," she adds. "I even got to be in their weddings. Maid of honor this fall."

"It's a good place to meet a husband," says Patti Humphries, who did. She and her husband, John, play for the Coors Light team in one of Prince George's County's several coed leagues.

Above all, softball is an extremely accommodating game, a bring-your-own-atmosphere kind of activity. Folks on the Coors Light team are straightforward about pursuing the game as an opportunity to meet members of the opposite sex. ("It's where I met eight of my girlfriends in a row," says Mark Franklin, who married No. 8.) Their pre-game repartee is friendly and quick.

On a recent night, the Coors group was playing the Chevy Chase Weasels (another of the joys of softball is naming your team). One of their players had a shirt that read Most Valuable Weasel. "Is this a good quality?" asked Lisa Boehme.

Later, when the Weasels' leadoff man dug, deeply, into the batter's box, Patti Humphries asked him if he needed a bulldozer. "We're planting petunias this year," Boehme called from behind the plate.

While sitting on the Coors bench makes one feel as though one has been dropped into the filming of a beer commercial -- except for the absence of beer, which is banned from most fields -- sitting in the bleachers while Unisys, the computer firm, has its corporate team on the field is like being surrounded by young suburban culture. There is a 1-year-old celebrating her birthday with pink and purple helium-filled balloons while her mother reminisces: "One year ago at this time I was in labor. And I'd been in labor for seven hours." There are snapshots of new furniture and wallpaper and reports on the progress of other women's pregnancies.

"It makes a good social environment," says Bob Donovan, a sales representative and the team's captain. "We have social events outside of softball. Cookouts. Baby showers."

"If you get a team that doesn't make it a family-oriented thing you get all kinds of problems with the wives," says Tom Bresnahan of Edgewater, who coaches Elliott's, a flooring company in Prince George's. "And we got enough divorces in this country."

No one has taken the dictum that the family that plays together stays together more seriously than the Baczynski family of District Heights. Bob Sr. is the designated hitter, Bobby Jr. plays shortstop, and sisters Ruth, Karen and Patti play outfield, first and second base. Ruth's boyfriend, Mark Mikalajunas, plays left and mother Sue and daughter-in-law Leslie split the scorekeeping duties. The family team is called B&B Masonry after the Baczynskis' bricklaying business.

Most coed leagues require five players of each sex to be on the field, dictate that a woman must follow a man in the batting order and allow women to hit a smaller, livelier ball. This might breed a certain chauvinism among the men were it not for one simple fact: The balance of power in these leagues lies with the women.

"The guys tend to cancel each other out," Karen Baczynski says. "If you don't have good girls, then you don't have a good coed team." And local college and high school programs have developed scores of talented female players. On the Baczynskis' team it is the women who wear the knee braces, and on one recent evening, it was the women, and only the women, who hit balls over the outfielders' heads.

The importance of women players helps make softball what it is, a democratic obsession, open to one and all.

"You know," says Lisa Boehme, who is in her late twenties, "playing softball is the most consistent thing I have done in my whole life. I used to play four nights a week, but your responsibilities change. But I have friends in their forties who play a couple of times a week and I anticipate doing the same thing."

"People who don't play softball marvel that you can play so much," Martha Lorenz says. "I think eventually people might get softball burnout but I haven't hit the wall yet."