(FORTUNE Magazine) – -- Who's the most nervous person in corporate America right now? The staff member who, back in July, forgot to make reservations for December's office party. Choice New York City spots, such as the Four Seasons, where food and drink can cost $150 per person, are booked solid. No amount of pleading can blast open the reservation lists of maitre d's who ask, politely, if monsieur or madame has perhaps considered Wendy's. Bristol-Myers had the good sense to claim the Waldorf-Astoria's Grand Ballroom 364 days in advance -- the day after it last partied there. Over 75% of the Waldorf's clients reserve as early, to be assured a spot. At Le Cirque, where reservations for ordinary dinners sometimes are made two to six months in advance, the owner advises reserving December parties in April. This season Washington's restaurants are also hard to crack. Reporters and observers attending the Reagan-Gorbachev summit are pushing capacity to the limit. The Madison Hotel, where the Soviet delegation is scheduled to be bivouacked, recently doubled its function space and still has only a few openings left for the month of December. Revelers will pay around $60 per person for a four-course meal. Outside the Northeast, making late reservations is easier. In Dallas, companies still can reserve a night at Southfork, legendary home of TV's Ewing family. Ford, Frito-Lay, and Toyota will visit the ''Most Famous White House West of D.C.'' in December to host parties that go for about $52 per person. Extras -- such as live steers, an actor impersonating Larry Hagman playing J. R. Ewing, and ''Miss Trixie, the World's Bawdiest Saloon Girl'' -- add to the tab.

In Boise, Idaho, the 1,000-person headquarters staff of Boise Cascade need not worry about getting a late booking. ''Our party is in the cafeteria,'' says spokesman Bob Hayes, ''and reservations aren't required.''