Hundreds of Montgomery County cat owners, with their pets on leashes or tucked in shoeboxes and cages, or wrapped in towels and blankets, waited for as long as three hours yesterday at the animal shelter in Rockville for free rabies vaccinations for their cats.

At 5:30 p.m., one hour after the free clinic was supposed to have ended, harried workers at the shelter were still vaccinating reluctant cats.

For a while, Director David E. Wheeler said he expected the shelter would run out of vaccine before the people with cats still lining up in the parking lot reached the shelter door. But about 7:30 p.m., the last of 1,333 cats was vaccinated.

"It's wonderful to get a whole lot of them vaccinated," said Wheeler, who spent most of the afternoon helping cat owners carry cages and boxes back to their cars. "I just wish they hadn't all come in at once."

The cat owners converged on the shelter after the Montgomery County Council on Tuesday mandated rabies shots for cats to prevent an areawide outbreak of rabies among wild raccoons from spreading to domestic pets. (Dogs already are required to have rabies shots.) Yesterday was to have been the last day cats could get free injections from the county, but the line was so long -- some people who arrived at 2 p.m. did not leave until about 5 p.m. -- that Wheeler scheduled another free clinic for Sunday, Dec. 5.

Once inside, the pet owners found the injections took only a split second. But the parking lot and driveway outside was turned into a feline zoo, packed with hundreds of cats, many howling and meowing loudly from boxes. Most people brought two, three or more cats.

"This is something I've never seen the likes of before in all my life," said Elizabeth Wiehle, a Boyds resident who brought her nine cats in cages and boxes and waited in line for three hours.

"I think next time I'll take her to a private vet," said Potomac resident Judy Iura, who waited 2 1/2 hours with her daughter Amy and their two cringing felines, Stravinsky and Wolfgang.