DINNER AT 11 p.m. Tango dancing until 1:30 a.m. A cafe stop at 2. In bed by 3.

This was just our second night out in Buenos Aires, and we were following the lead of our hosts, Luisa and Alejandro, friends we met a few years ago in Seattle. It was clear we early-to-bed Seattleites had a few things to learn about Latin life: Meeting for "coffee" might mean gathering somewhere around 6 p.m. No one eats dinner before 10 p.m. And when our friends suggested we meet at their apartment one day around noon, it was not for breakfast or even lunch, but mate, a tea-drinking ritual as sacred to South Americans as our daily stops at Starbucks.

Picture yourself hooked on a hot, herbal drink as popular and portable as a latte. But instead of a paper cup, you sip from a "mate," a hollow, pear-shaped gourd packed with a mildly stimulating dried, chopped leaf from a South American holly tree. The gourd, stuffed with the green tea called "yerba," travels with you wherever you go. Along with it, you carry a silver straw-like utensil with a bulbous filter on the end and a container of hot water.

An invitation to drink mate is a sign of friendship, not to be refused. Unlike a latte, mate is seldom served at restaurants or cafes; rather it's sipped and shared among friends or family during breaks at the office, on the bus, behind the computer terminal or in the park. Argentina is believed to be the largest consumer of yerba mate. It's also popular in Uraguay, Paraguay and parts of of Brazil. Now mate is catching on in Seattle, although it may still be a while before we see our neighbors walking down the street carrying gourds and Thermos bottles.

"It's kind of the rage right now," says Paul Stolp, grocery manager at Madison Market Natural Foods, which stocks an organic yerba mate called Guayaki, shade-grown in Paraguayan rain forests. "A lot of people are kicking coffee and going to this instead.

" Mate contains a natural alkaloid called mateine, a mildly stimulating relative of caffeine that tends not to produce side effects such as nervousness or sleeplessness. Mate contains B vitamins, minerals, amino acids and antioxidants, so is generally recognized for its nutritional benefits as well. A cup of mate is thought to have about half the equivalent caffeine level of a cup of coffee although "the exact level is a cloudy issue," says Chris Mann, co-founder of California-based Guayaki Sustainable Rainforest Products, an importer and wholesaler of mate for growers in Paraguay.

"It's definitely something that's a Seattle kind of drink. It induces mental clarity and sustains energy levels. But unlike with coffee, you don't get the crash," says Mann.

The Guayaki people of Paraguay began drinking mate centuries ago to boost the immune system and aid digestion. It was commercialized by 17th-century Jesuit missionaries and is now a huge industry in South America.

"Only a small percentage of people here know about yerba mate," says Joel Dahl, grocery manager for Puget Consumers Coop, where Guayaki mate has become the chain's best-selling tea. "But the people who do buy it know about its benefits."

The modern mate drinker can buy the tea in bags (around $5.80 for 25) or loose (about $13 a pound), and brew it like normal tea or in a coffee press. But with your own gourd and a bombilla (a few stores in Seattle sell them, including the Ballard Market and Market Spice in the Pike Place Market, or they can be ordered from Guayaki's online catalog), you can follow in the footsteps of thousands of South Americans who sit behind their desks and cash registers sipping mate according to ancient rituals.

Our Argentinian friends first introduced us to mate while they were living in Seattle. We had finished dinner at their Queen Anne apartment when Ale reached for his small gourd and filled it with yerba sent to him in a 5-pound bag by his mother in Buenos Aires.

Mate is an acquired taste; at first sip, our lips burned and the flavor was smoky and bitter. Ale played the role of "cerbador" or server, taking responsibility for filling the gourd with the tea, heating but not boiling the water in a kettle and pouring it into the vessel. After a few sips, we passed the gourd back to him for a refill of water. When you've had enough, a simple "Gracias" or "Thank you" is the signal for the cerbador to pass you by.

"Drinking mate is, in a way, like sharing coffee with friends, but it creates a more intimate atmosphere and it requires more time," Luisa told us. "You can't share mate in a few minutes. Unlike coffee, it's not something to do in a hurry."

Carol Pucci is deputy business editor at The Seattle Times.