The American Society for the Prevention of Cruelty to Animals says the cost of maintaining a large dog can run about $660 a year. That would cover food, routine veterinary visits and miscellaneous expenses, such as leashes, bedding, toys and treats. A medium-sized dog can cost about $450; small one, $300.

Cat costs are nothing to shake a paw at either, with maintenance running about $350 a year each, the New Yorkibased society estimates.

Gail Buchwald, an ASPCA vice president, said it's an acceptable trade-off for most people.

"I know that $600 — or even $300 — sounds like a lot," she said. "But of course, what you get back from a pet is priceless."

That's what Emily Foley, a public relations specialist in Royal Oak, Mich., is discovering with her first pet, Suds, a black-and-white kitten.

"We had no idea he'd become a line item in our monthly budget," Foley said. "We've spent $500 so far for shots, neutering, declawing, flea stuff, things like that. It really adds up."

Then, of course, there's the lure of cat accessories.

"I didn't know what cats like, so I picked out one of everything," Foley said. That included a modern litter box for $30 and an ID tag. "I also bought him a bed, which he's never used, and a 'kitty condo' with lots of levels for climbing, which he's never used except to scratch a little."

Foley said that she's cut back on a planned vacation because of her cat expenses, but that it's worth the investment when "you come home from work and you're bummed out about whatever, and there's Suds doing backflips and racing around and then wanting to cuddle."

Carol L. Bowers, Web manager for the Society of American Military Engineers in Alexandria, Va., has two dogs, two parakeets and two finches. Keeping the birds is easy, requiring just a bit of seed, the occasional toy and paper towels for cage liners.

But Jag, a 9-month-old mixed pug-boxer, is a big eater. Magic, her 10-year-old mixed Labrador, has had surgery twice for cancer and is on a special diet.

The cancer surgeries cost about $3,000, while repair of a torn ligament that Magic suffered several years ago was an additional $1,800, Bowers said.

Then there are the expenses you don't anticipate, like steam-cleaning the home after one of the dogs comes in with a bad case of fleas, she said. Or how, on one recent morning, Jag "got into my wallet and ate my ATM card and a dollar bill."

Still, Bowers said paying for an animal's needs is what pet ownership is about because "when you agree to take on the responsibility for an animal, you can't bow out when it's tough."

In exchange, she said, she gets "unconditional love, companionship and entertainment — definitely entertainment."

When it comes to cats and dogs, doing some research before adopting or buying can help a family estimate costs over a pet's lifetime. Families should start by researching various breeds to find a pet compatible with their lifestyle.

Daisy Okas, assistant vice president for communications with the American Kennel Club in New York, said you should ask yourself whether you want "a running partner" or "a dog that will cuddle on the couch."

She also pointed out that expenses can be much higher for a city animal than a country animal.

"In New York, the annual vet examination can cost $300," she said. "In a rural area, it's probably close to $75."

Pet owners also need to consider obedience training classes, especially for larger dogs, and walking services if their job keeps them away from home for long hours.