Macau, a Portuguese enclave on the other side of the mouth of Guangdong's Pearl River from Hong Kong, has always been the British territory's sleepy sister--its economy fueled by tourism and casino gambling. Both Hong Kong and Macau are about to be returned to Chinese sovereignty--Hong Kong in less than two months, and Macau in just over two years--but as these twin deadlines approach, the differences between the two are striking. While there are major political conflicts in Hong Kong, the economy is booming, the property market is strong, violent crime is in decline, and about half the populace tell pollsters they are confident about the future.

In Macau, there's a property crash, rising crime by gangs known as triads, and lots of anxiety about the 1999 hand-over. This despite the fact that Portugal, unlike Britain, granted its colonial subjects full citizenship, meaning any Macanese can migrate to any country in the European Community. Not so long ago, Macau wasn't gloomy at all. The quaint city of 440,000 has long been a tourist's delight, with its famous cuisine, brightly painted Iberian architecture, and relaxed pace. But then came the crime wave. It began six months ago and has so far killed 14 people. Macau development officials don't want to talk about it: ''That's a touchy subject I'm not sure we can address,'' says one with a laugh.

But Tourism Dept. statistics tell a worrying story. While overall tourism increased in 1996 by 5%, the December figure, which came after the upswing in triad violence began to make the news, was down 5% from a year earlier. The falloff in visitors from Hong Kong, which accounts for over half of Macau's tourism business, has been even more pronounced: 21% over the same period.

According to the police, the growing violence in Macau can be traced to both a slowdown in the casino business and, ironically, police success in cracking down on the triads. ''The cake is getting smaller, so the gangs are having to fight to keep their piece as large as before,'' says one security official. Inside the gaming houses, the slackening sure isn't noticeable. The tables are crowded and the slots busy at the downmarket Casino Lisboa, just a block from the latest shooting, while prostitutes in tight miniskirts whisper propositions.

The only indication of something amiss is the armed Macau cops outside the entrance to the building, eyeing everyone who comes or departs. For rollers high and low, worries about Macau's future--or present--seem far off. Gentlemen, place your bets. In 1985, when China inked the deal with Portugal to assume sovereignty in 1999, some Hong Kong developers, led by Hopewell Holdings Ltd. and Shun Tak Holdings Ltd., embarked on a building boom. They assumed that closer links to the fast-growing city of Zhuhai across the border would mean rapid expansion.

But the boom may have been built on a mirage. Hopewell, for example, is having trouble with its largest single property project, a 1 million-square-foot joint venture with Shun Tak called Nova Taipa Gardens. A Hopewell spokesperson says phase one--13 of 34 planned high-rise residential blocks--is complete, but only eight of the blocks are fully sold. The finished project will include residential units, a convention center, and a hotel, but analysts express skepticism about its completion date and profitability.

And as for the market in general, Michael Green of Salomon Brothers in Hong Kong says the problem of overbuilding won't go away for a good long time: ''I don't know of a bigger oversupply of property anywhere in the world.'' So Macau may have to get used to being in a funk.