EVERY early evening 15 or 20 people wearing all kinds of pajamas can be seen exercising, dancing and socializing in the commercial plaza near Tianlin neighborhood in Xuhui District.

Every evening 57-year-old Xu Li, already wearing her PJ bottoms, puts on lipstick, pulls on her pajama top and takes a 15-minute walk down the street to the plaza, along with her next-door neighbor.

She is among more than 30 men and women, mostly retired, who consider their jammies perfectly presentable for street wear. Many consider wearing PJs in public to be one of Shanghai's charming old customs.

As most are women, fashion is a common topic, including where they get their nice jammies with cutsy colorful prints (like teddy bears, kitty cats and flowers), different weights for different seasons, and so on. Some are Chinese designer brands of shui yi (literally sleep clothes) or pajamas.

Bystanders gather, including women in pajamas with high heels and makeup.

Some people wear their PJs to the nearby supermarket.

Then there are older men who walk about in rumpled pajamas that have seen better days and need a good washing.

But Shanghai's pajama party is supposed to end.

In some districts, neighborhood committees have recruited volunteers for the anti-PJs-in-public patrols, "the pajama police." They try to persuade residents that it's uncool to wear their jammies in public.

No pajamas in public, be civilized for World Expo - that's the slogan. But it's not compulsory.

Those neighbourhood committee officials consider wearing pajamas in public, an old Shanghai neighborhood tradition, to be an embarrassment, especially as the six-month World Expo 2010 opens in Shanghai on May 1.

Wiping out pajamas on the streets is part of the public etiquette campaign for the Expo. Official image-makers don't want the cosmopolitan city to "lose face" in front of foreigners by appearing less than sophisticated.

The same goes for generally uncouth behavior, such as spitting, littering, shouting, queue jumping and pushing, and other irritants. Down come the bamboo laundry poles in areas where Expo visitors are expected.

It must be said the situation has improved on all these fronts.

Some Chinese find the big push to prettify and change longtang (lane) wear and traditional laid-back style offensive, especially as the city gussies up to please Expo visitors.

The campaign to jettison jammies in public has created a stir. Some support the idea, others say they should be able to wear whatever they like and the government should not interfere.

"It's not good to exhibit private things like pajamas in public, but it's really just an individual freedom that should not be disturbed," says Lu Gusun, a leading lexicographer and famous foreign language professor at Fudan University.

Lu says it might be better to have pajama parties for the Expo rather than banning the attire in order not to lose face in front of foreign visitors.

Many local Netizens also consider the campaign too sudden and unenforceable, noting the habit goes back more than 70 years to the time of more casual living in longtang. People in PJs regularly went about on their errands in the neighborhood.

Today many shops sell PJs that obviously are for outwear wear, with mannikins wearing jammies, fashionable shoes and hats, and holding handbags. 'Mom and I argue about pajamas' Linda Lu, 27, returned last summer from Australia with a master's degree and, of course, moved back home.

She finds it difficult to communicate with her parents, whom she considers old fashioned and stuck in the old days.

She and her mother often argue about wearing pajamas on the street. Through her years in Australia, Lu got used to changing into pajamas before going to bed and wearing them just as sleepwear, not casual wear.

But as soon as she gets home from her job in a real estate company, her mother wants her to put on her pajamas, saying, "You shouldn't wear nice work clothes when you're around the house or the neighborhood."

She is obedient.

Her mother also doesn't allow her to put on street clothes when she leaves the house to run errands after work.

"When I first went to Australia, I wasn't aware of the different habits and wore pajamas to the school dining hall," says Lu. "My classmates were really surprised and asked whether I had just come from a pajama party," Lu recalls. She was deeply embarrassed, even more so when classmates asked why Chinese people wore pajamas on the street.

"I feel embarrassed wearing pajamas today, though I know it's common," she says. "But my mom would just call me eccentric if I refuse to wear them. She says changing clothes is a waste of time and energy."

Her mother recalls the old days when she even wore her pajamas when she rode the bus.

"I like the idea of banning PJs, but it's difficult to persuade my mom. After all, she has lived that way for more than 50 years and she's not going to accept sudden change," says Lu.

'I live in my pajamas' Like Linda Lu's mother, 69-year-old Mao Yindi can't believe she's not supposed to wear her pajamas when she leaves the house.

"I don't wear these pajamas for sleep," she says. "My son just got me a new set for the winter, and they are really warm," says Mao, who has four sets of PJs for different seasons.

"When I was little, we would wear the same shirt for two or three days. Only rich people had changes of clothes, not to mention pajamas. Now it's better and we have so many sets of pajamas."

Mao lives alone in a shikumen (stone gated house) in a long and twisting longtang in Hongkou District. The lane is secluded.

She lives on the second floor and shares the kitchen and shower with another family.

She's at home most of the time and wears her pajamas all day. She wears them to go out in the lane or the street to buy vegetables, get her hair cut, visit small shops or eateries.

She might wear a newer set if she goes out to a restaurant.

She only wears street clothes when she has to go far away.

For Mao and her neighbors, the longtang and neighborhood are an extension of their domestic space and private lives.

"I wouldn't wear pajamas to work - that's public," she says. "I wear pajamas to hang out with my neighbors or buy household necessities and those are all part of my domestic and private life."