When Chicopee, Mass., gives a party, the centerpiece is apt to be a 25-foot-long, 230-pound kielbasa.

Chicopee, which has been sponsoring its kielbasa festival since 1974, wants the world to know that it makes more of this spicy sausage than any other city in the United States. And, lest you forget, there is the world's largest kielbasa to move your mind in the right direction.

That's the way they do it out in the heartland.

Here in Washington we, too, have parties with a purpose. Some are fun: birthday celebrations, parties for newlyweds, costume parties to celebrate Halloween, a tea dance for Valentine's Day. Some are for a good cause, to raise money for a disease, or the symphony or the opera, a tax-deductible chance to put on your best and see who else supports your favorite charity.

And, of course, there are the political fundraisers where guests must be told in advance what they're getting into -- how else to explain the picking of their pockets as they enter the door?

Then . . . then . . . there are those endless Washington parties where the real purpose is shrouded in mist and mystery.

Did Mr. C invite you to dinner because you share an interest in grouse shooting, or because you're on the Senate Banking Committee? Which of Mrs. A's clients wants something from which of your clients?

Rarely are people honest enough to hang The World's Largest Piece of Legislation in one corner of the room to remind guests why they are being fed smoked salmon and champagne. And when was the last time you saw a Giant Trade Agreement used as a centerpiece on an embassy dinner table?

When the social forms are converted to the use of business, the result is a succession of dreary dinner parties. It is the bit players who suffer most, the husband or wife dragged along to keep up the pretense that this 8 p.m. business meeting is actually a cozy dinner among friends.

"Gruesome," says one embassy wife, describing what she calls "single-issue" dinners, where all the guests have been rounded up to discuss some current event.

And does she try to liven things up when it's her turn to entertain?

"Absolutely not. I give up on it and invite the people I'm supposed to invite. I don't try to make it fun and interesting because the people would resent it. They aren't coming to have a good time. They're coming to conduct business."

"The food is almost always good and the setting lush," says another victim. "And why not? Both are usually being paid for by someone else -- some country or some company. But those dinners are always boring. There's never an element of risk, of surprise. No one gets drunk and makes a scene. People are too wary to let go.

"I used to dream that I would sit next to someone who would tell me everything there was to know about life in a medieval French monastery, or the best way to train a gun dog. But nothing unexpected ever happens. Or if it does, it's a fallen souffle or a dribbly mousse, neither of which are much fun to gossip about the next day."

Washington host/esses are not likely to change tactics, inviting everyone to come to an Immigration Reform and Control Act Festival, or a Generic Drug Bill Party, but the conviction that a party with a hidden purpose can't be fun guarantees that it won't be. If even the partygiver despairs of having a good time, what possible hope is there for the guests?

If you must persist in making work out of what should be fun, do it with imagination:

*Think of the evening as two parties. At one party are those who work, at the other those who play. Seat the workers at one table, or, if that's not possible, lump them all together at one end of the table. Forget about man/woman, man/woman. It's as unnecessary as it would be at a board meeting and if you fill in with sacrificial victims, the workers won't notice anyway.

If you devote your attention to making sure that the tag-alongs have a good time, they won't care either. And if protocol simply will not allow such lumping, make dinner a buffet and let the workers find each other -- which, I promise you, they will.

*Make all your working parties lunches. No one is expected to bring a spouse to lunch.

*Hide one purpose behind another, by putting the workers in an appropriate setting so the evening can be fun for everyone.

If it's a wilderness bill you're interested in, move all your furniture into the basement, rent lots of large plants and serve a picnic on the floor; for an education bill, buy up lunchboxes, fill them with pa te's, cheeses, bread and fruit (wine in the thermos, please, not milk) and let people eat where and when they want; for a banking bill, stock up with phony money and raffle off dinner -- see who's willing to pay a million dollars for a chocolate mousse. Or install a gambling casino and check your guests for reckless tendencies.

If your only purpose is to improve your acquaintance with some White House aide, why in heaven's name do you think boring the person to tears will do it?

No one ever made a name as a brilliant host/ess by trumping along in the footsteps of bores. Anyone who gives a dinner out of a sense of duty should expect the guests to attend in exactly the same spirit.