TAEGU, South Korea -- By day, Lee Seung Seop wore a gray polyester uniform in his job as a repairman of industrial boilers.
But after work let out at 6 p.m., he would take off his uniform and head to a nearby Internet cafe. There, the 28-year-old would enter an enticing virtual world with saber-toothed dragons and purple-haired women in metallic bodices.
The evenings stretched into nights and the nights into the dawning of the next day. Lee sometimes forgot to eat. He didn't sleep. He came into work later and later until his boss fired him.
One night, after a 50-hour binge playing an online game called ''World of Warcraft," Lee collapsed and fell off his chair. He died a few hours later.
''He was so concentrated on his game that he forgot to eat and sleep. He died of heart failure brought on by exhaustion and dehydration," said Park Young Woo, a psychiatrist at Taegu Fatima Hospital, where Lee died.
More people drop dead while eating dinner than playing online games. But Lee's death this month gained widespread notoriety, bolstering fears among South Koreans that they've become hooked on the Internet.
South Korean authorities have linked several high-profile deaths to excessive Internet game-playing. Some believe that cyber cafes have in effect become the opium dens of the 21st century, luring players into staying around the clock and disregarding their health and responsibilities.
In May, a 4-month-old girl left alone at home in Inchon died of suffocation while her parents were playing at an Internet cafe.
''We were thinking of playing for just an hour or two and returning home as usual, but the game took longer that day" -- that's how a police officer, paraphrasing from the parents' words, was quoted in newspapers. The parents were charged with involuntary manslaughter, police said.
Authorities seem mindful that they have a social problem in the making. This month, the government-run Korea Agency for Digital Opportunity & Promotion began sending psychologists into cafes to warn players of the dangers. Players also are being handed questionnaires asking, for example, ''Do you sometimes wish that what is happening in the games was your reality?"
Son Eun Suk, one of the psychologists who visits cafes, says online gaming is potentially a bigger social problem than drugs or booze because people are unaware of their addictiveness.
''Parents and teachers lecture against drugs and alcohol, but they are very open to the Internet," he said. ''They think their children are learning something about computers, and they allow them to play from a very young age."
South Korea boasts of being the most wired country in the world. Nearly three-quarters of its households have broadband connections, whereas the United States remains at about one-third.
But by dint of their status in cyberspace, South Koreans may be providing the rest of the world with a scary glimpse of the future.
The most seductive games are known in the industry as massively multiplayer online role-playing games, in which more than 100,000 people around the globe can play at the same time.
In these virtual worlds, participants create an online persona that develops skills and can climb the social ladder -- from serf to knight, say, with medieval Europe being a popular theme -- and acquire virtual treasures such as a magic sword or castle.
South Korea's online gaming industry brings in $1.2 billion a year and has been growing about 25 percent annually, according to the trade association in Seoul. The country is pushing exports of its games to the United States, China, Japan, and other markets.
South Koreans are considered the world's most avid online gamers by far. In fact, a poll the government published in May found that online activities are more popular than television among South Koreans ages 9 to 39.
Although people of both sexes and all ages play, the most prevalent are lower-middle-class men in their 20s with unsatisfying professional lives. Lee was a case in point. He grew up in Taegu, South Korea's fourth-largest city. His family was poor and lived in a shop they ran, a relative said.
Lee attended a vocational college near home and after graduation moved in with a married older sister and her family. He worked in a drab, walk-up office that looked like a time capsule of the 1960s, with harsh fluorescent lighting and curling linoleum.
''He seemed like a very normal and ordinary guy," said Park Chul Jin, the office manager. ''There was nothing odd about him, except that he was a game addict. We all knew about it. He couldn't stop himself."
Park Chul Jin fired Lee about six weeks before his death, after repeated warnings about being late. Around the same time, Lee split up with a girlfriend, who was a fellow gamer, co-workers said.
The last weeks of Lee's life were spent largely in an Internet cafe. The PC bangs, as they're called here, are homes away from home for many South Koreans. The cafes typically charge just $1 an hour and are open around the clock.
Lee died on a Friday night. He had been at the keyboard since Wednesday.
''He just fell off his chair. His eyes were open, he was conscious, but we could tell right away that it was serious," said Kim Jin U, who was there at the time.
An investigation attributed the fatality to excessive game-playing. But gamers said Lee's behavior wasn't different from others'.
''If you could die from playing too many games, I'd have been dead long ago," Kim said. ''I just can't believe it."