"Dear Sir," the letter began, "I'm sorry to part with my dog, but as I told you on the phone, she is sick and I do not have the money to get a vet. I have had her for eight years . . . She's a smart dog and a clean dog."

Anna Pierce, a 78-year-old widow, attached the letter to her dog Tippy's collar just before the D.C. Dog Pound picked up the animal on May 23. Later that day, Tippy was dead.

"I wrote the letter because i didn't want them to think I was too cheap to get a vet," said Pierce, who lives on a fixed income of $300 a month. "I just couldn't afford it."

More and more pet owners in the nation's capital, citing the rising costs of veterinary care and pet food, are turning in their animals -- especially dogs -- to the D.C. pound, saying they cannot afford to keep their pets.

On a recent Saturday, 70 dogs were brought into the pound, and all of their owners cited economics as the reason, according to the facility's director.

"We're just swamped," said Ingrid Newkirk, director of the shelter on New York Avenue NE. "As the economy has gotten worse, more people than ever before are coming in, saying they can't afford to keep their pet. In the last few years, I've seen a notable increase in this. Now, it's a matter of course."

Older people, said Newkirk, are especially vulnerable. "They become very upset and cry," she said. "It's really bad."

In years past, said Newkirk, "we'd get more varied reasons for giving up a pet, the animal bit a family member: the apartment won't allow pets or the animal was hard to handle. Now, 99 percent of the time, it's economics."

"People tend to acquire pets impulsively, said John Hoyt, president of the Humane Society of the United States. "Then, all of a sudden, they discover it's more expensive, especially with inflation to reckon with."

The D.C. shelter receives about 700 animals each month: 400 dogs, 250 cats (which are cheaper to keep) and a number of miscellaneous pets, such as goats, chickens and birds. Most of the animals are destroyed, Newkirk said, because the facility has a hard time placing them for adoption.

The pet inflation problem does not seem to be as dramatic in the suburbs: none of the pounds in the Maryland and Virginia suburbs reported a recent upsurge of owners unable to afford their pets.

"We all know D.C.'s a very expensive place to live," said John Hoyt, "I'm sure it's true with pets also."

According to a recent survey, veterinary care in metropolitan areas like Washington are considerably higher than in rural areas.

"An informal survey of more than two-dozen veterinary clinics in the area showed that the cost of sterilizing a 32-pound female dog ranged from about $60 to $100. Once outside the city, though, the price often dropped dramatically. One clinic in Oxon Hill, for example, charges only $35 for the procedure.

"Veterinary care is expensive," said Dr. Candace A. Ashley, director of the Animal Clinic of Anacostia. "But it's like taking your children to the pediatrician. Serious pet owners are able to make responsible adjustments to pay for it."

Newkirk says the bills may be inflated. "The actual cost of a shot may be $1, but a veternarian might charge $6 to $17 for the same shot."

Ashley defends the medical costs, saying the veterinary profession has gotten "more sophisticated" in recent years. "It's like everything else going up," she said. "Suture material, needles, anesthesia, higher salaries for employes. Veterinarians are charged the same for supplies used by M.D.'s."

According to Hodge, the single greatest expense to a pet owner is food. "the average American pet owner will spend $375 a year to maintain a medium-size dog, with a minimum of veterinary care," he said. If the dog lives to be 10 years old, the total cost could run more than $4,000.

"In the last five years, the increase in pet care costs have been incredible, particularly in dog food," said Sandy Mejias, owner of the Old Town School for Dogs in Alexandria. For example, she said, a 50-pound bag of Science Diet dog chow sold for $23.26 in her small pet store three months ago. ago. Today, it's $26.19. Three months ago, a 20-pound bag of A & F dog food sold for $10.50; now it's priced at $12.90.

A Safeway spokesman said the cost of dog food in that larger chain increased about 5 percent over the past year.

"It's like the price of gas," said Edward Tuck, owner of Animal TV Trainers in Washington. It's an initial shock, but you make whatever sacrifices are necessary."

Tuck said the cost of leather leashes and collars has nearly doubled in the last few years, as has the cost of a dog license in the District of Columbia. lLast year, a license cost $4; this year, it's $8.

In response to the high cost of caring for a dog, the Tail Waggers Animal Clinic in Washington has begun offering cut-rate outpatient services to low-income pet owners. "All we want to do is service Social Security people," a clinic spokesperson said yesterday fearful that any publicity would draw more affluent owners "who don't belong here."

Yesterday morning, three men arrived at the D.C. Pound, accompanied by a frisky, honey-colored dog. The animal bore a cut on its side, and the men said they didn't want to pay to have the dog "fixed." A technician, who was standing nearby, said, "Between the three of you, you can't afford a vet?" The men shook their heads, and said they wanted to trade in the ailing dog for a puppy.

"It's really disgusting," Newkirk said, complaining that some owners simply fail to take into account the cost of pet care. "We've become a slaughterhouse for frivolity."