As retail rents in the city skyrocket, restaurants are increasingly using their upstairs and downstairs space for patrons, as well as opening extra bars within their venues to boost revenues and seeking new forms of financing, brokers and restaurateurs said.

“I can’t remember a more competitive restaurant environment in New York in the last 20 years,” an industry veteran who owns an eponymous restaurant in TriBeCa, Dennis Foy, said. “More people are having to do other things to supplement their revenue.”

Asking rents for retail space in Manhattan have increased by double-digit percentages for the last several years. On Madison Avenue, one of the priciest retail corridors, rents leaped more than 14%, to $1,091 a square foot, at the end of 2007 compared with the year earlier period, according to Cushman & Wakefield. Rents also rose by 14% on the Upper West Side, to $336 a square foot at the end of last year.

While there is increasing concern that the economy may be headed into a recession, and that rents could begin to drop, so far industry experts say they have not seen any slowdown.

“Manhattan’s retail market is an anomaly,” the COO of Cushman & Wakefield, Joseph Harbert, said when the firm released its fourth-quarter numbers.

Some of the restaurants struggling to pay high rents have come up with unique strategies. Hill Country, the Texas-themed restaurant, bar, take-out, and music venue that opened last June on East 26th Street, is just one.

Instead of taking the 10,000 square feet of ground floor space the owners originally wanted, they chose a two-level retail space with 5,000 square feet on each floor.

“It took two years to find the appropriate space,” the broker who represented the owners, Jason Pennington of Butler Kane, said. “It was just cost prohibitive.”

Hill Country added a bar in the front of the space, a streamlined take-out operation, a live-music venue downstairs, and a merchandise area near the cash registers. “This is what a lot of restaurants are having to do,” Mr. Pennington said. “They need multiple revenue streams — two, or sometimes three.”

The design of the upstairs and downstairs spaces can make or break a restaurant because New Yorkers are notoriously finicky about where they eat, the head of retail at Prudential Douglas Elliman, Faith Hope Consolo, said.

“We used to call lower levels with no light basements,” Ms. Consolo said. “Now we call it a concourse. It isn’t traditional for restaurants to seat people downstairs, so you have to create just the right environment to get them down there.”

Ms. Consolo said she recently brokered a lease for Morton’s: The Steakhouse at 345 Adams St. in Brooklyn. The restaurant is taking 6,000 square feet on the ground floor and using another 7,000 square feet downstairs for catering.

She also brokered the lease for Shelly Fireman’s Trattoria La Tradizionale at 41 W. 57th St., which she said was especially attractive because it already had a built-in mezzanine from its previous incarnation as a deli.

“All these additional spaces for events and catering — that’s what they call gravy,” she said. “It’s all profit. That’s the only way they can offset the rent.”

Ventures are also seeking reprieves from high rents by making deals with developers who are looking for signature restaurants for their new residential buildings or hotels.

“Restaurants cannot keep the pace with the kind of rents that the primary landlords are asking,” a senior managing director of JDF Realty, Leslie Siben, said. “You are seeing Medici-style owners of buildings becoming partners to restaurants. They give them sweetheart deals.”

Another consequence of the high rents is the proliferation of wine bars, the New York editor of Zagat Survey, Curtis Gathje, said.

“Real estate is playing havoc with opening new restaurants in this town,” he said. “Everything that is opening seems to be wine bars and small-plate restaurants.” Wine bars and tapas-style restaurants often generate significantly more profit than traditional restaurants because they have much less overhead, and small plates can quickly add up to large bills.

“People will readily pay $12 for a glass of wine and order small plates, which, surprise, quickly add up,” Mr. Gathje said.

Among the newest openings Zagat Survey is reviewing are the wine bars Bacaro in Chinatown, Gottino in the West Village, Riposo 72 on the Upper West Side, Solex in the East Village, and Xai Xai in Hell’s Kitchen.