This city has become a front line in a generational battle for jobs, as older workers increasingly compete against applicants in their 20s for positions at supermarkets, McDonald’s and dozens of other places. And older workers seem to be winning.

With unemployment at a 26-year high and many older workers chasing entry-level jobs like those they held a half-century ago, 70 has become the new 20, as one economist put it.

Millions of older Americans have delayed retirement because of plummeting 401(k)s, soaring health costs, a sense that Social Security benefits alone are too little to live on or all of the above. This delay, economists say, has made it harder for millions of young workers to climb onto the first rung or two of the career ladder, especially since many employers favor hiring applicants with a track record.

“The boomers are staying in the system longer, and that’s clogging the system,” said Mason Jackson, president of Workforce One, a federally funded agency that helps Broward County’s unemployed. “Many want to retire, but they can’t.”

He characterized the dominant attitude among employers now as: “In with the old and out with the new.”

Along the ocean beaches and the Intracoastal Waterway here, retirees in condominiums have long coexisted with a much younger generation, but in the depressed job market, tensions have swelled as each group complains that employers improperly favor the other.

Since losing his job as a carpenter 13 months ago, Arnold Stone has applied, without success, for jobs as diverse as grocery bagger and construction worker. In his mobile home one recent morning, Mr. Stone, 69, tanned and vigorous, displayed hundreds of résumés.

“I’m sure age comes into play,” he said. “The problem is with seniors, nobody wants to hire them.”

That same week, Farah Titus, 25, crisscrossed Broward County in her 11-year-old Toyota on her daily job search. She pointed out a J. C. Penney store, a Macy’s and a Wal-Mart where she has applied to no avail.

“It’s hard to break in,” said Ms. Titus, a part-time nursing student who said she hated asking her father for money. “If you have experience, they put you on the top of the pile.”

The latest reports from the Bureau of Labor Statistics buttress her view. The number of employed workers ages 16 to 24 has fallen by two million over the last two years, to 18.3 million, while the number of Americans 65 and over who are working has risen by 700,000, to 6 million.

“In a bad labor market, different groups perceive that they’re being discriminated against when the real problem is they’re being mistreated by the overall economy,” said Teresa Ghilarducci, an economics professor at the New School of Social Research and author of “When I’m Sixty-Four.”

The proportion of older Americans who hold jobs has also risen strongly — 16 percent of Americans 65 and over had jobs last month, up from 11 percent 10 years earlier. But for workers age 16 to 24 the percentage with jobs has fallen to 49 percent, from 59 percent a decade ago. As for Americans age 25 to 29, 74 percent now have jobs, down from 81 percent a decade ago.

“Younger people are taking an extreme pounding,” said Andrew Sum, director of the Center for Labor Market Studies at Northeastern University. “It’s worrisome because they’re not developing the experience and the soft skills that they’ll need and the nation’s economy will need.”

The greatest employment losses, he said, are for young males with little or no college. Many found jobs when the economy was robust, but they were often laid off first in the downturn, and they are having an especially hard time landing jobs now.

“I’m applying for low-wage jobs, and anyone should be O.K. for them, but I’m not getting to first base,” Jose Nieves, 19, said of the restaurant jobs he has applied for.

But many older workers say they suffer age discrimination, too. Mr. Stone is convinced that employers favor the young because they want to make sure their investments in training pay off for years to come.

Mr. Stone said he wishes he could retire but his retirement savings have nearly disappeared. He invested heavily in Enron before it went bankrupt, and his wife has had sizable medical bills.

“I need a job because at the end of the month, I’m lucky if we have $450 left,” said Mr. Stone, who worked 20 years as a carpenter and once even owned a construction company.

“People say there is no work to be had,” he added. “But if you’re over 50, you really have a problem, and if you’re 70, it’s especially hard.”

Eva Coffey, 60, from Springfield, Va., said that when she applied for a job as a bookkeeper and receptionist for an auto dealer, her interviewer showed no interest. The next person to be interviewed, she said, was an attractive woman in her 20s, and the interviewer was keenly interested.

“I’m not some young thing,” Ms. Coffey said. “When you go for an interview now, you’re always trying to come across younger because they’re concerned about your age. It’s a hard obstacle to overcome.”

Federico Barker, 76, a former real estate developer, has applied for so many jobs unsuccessfully that his friends urged him to lie about his age and change dates on his résumé. They are certain that employers favor younger workers.

Mahalia Joseph, 21, disagrees. She lost her job at a check-cashing company four months ago and has been rejected repeatedly for jobs in customer service and at hospitals.

“With the economy the way it is, they don’t want to hire people they have to train,” said Ms. Joseph, who plans to take courses to be trained as a hospital assistant. “They want people who are hands-on right away.”

Every day, young and old job seekers swarm to Mr. Jackson’s Workforce One offices, searching computer databases for jobs. Employers see strengths and weaknesses in each group, he said.

“Many businesses prefer older workers,” Mr. Jackson said. “They know they’re dependable, reliable. They show up, and somewhere along the line, developed customer service skills. Older workers take less sick days. Most sick days have nothing to do with being sick. Many nice days people call in sick to go to the beach.”

One category where young people have an advantage is technology jobs, he said. “If it’s a technology job, young people take to it as fish to water,” he said.

One of his assistants, Kelly Allen, chimed in that young people were used to communicating electronically — she held up an imaginary Blackberry and maneuvered her thumbs wildly. “Employers like that older workers are used to dealing with people face to face,” she said.

Maria Brous, communications director for Publix, one of Florida’s largest supermarket chains, said older workers had important expertise, but younger workers had technical skills and were creative problem-solvers. Publix hires both young and old employees, she said, because they complement each other.

Wendy Smith, 23, says she has seen yet another type of discrimination in applying for administrative jobs. Potential employers tell her she needs three or four years of experience.

“They don’t want you to be too young, and they don’t want you to be too old,” she said. “They want you to be just right.”