During the preholiday crush last December, a computer maker asked staffing company Adecco SA for 300 additional factory workers — immediately. Using an instant-messaging program, Senior Vice President Steve Baruch tapped managers in three states to line up the workers within hours. If he had relied on e-mail and phone calls, Baruch says, the same process could have taken him as long as three days.

Instant messaging is invading and changing the workplace. Employees started to sneak instant messaging into the office in the late 1990s, but now more companies are endorsing it. Faster and more casual than e-mail, instant messaging can foster broader collaboration among employees even as it further blurs the boundaries between work and life.

Instant-messaging programs allow users to organize contacts into "buddy lists" and see who is online and available to chat at any given moment, worldwide. With most IM programs, users can start real-time conversations with one or more contacts, including multiple participants simultaneously. Sending a message opens up small windows on the participants' screens where users can type their chats. Most programs also offer file-sharing, voice and video features. IM can be used on computers and on wireless devices like cell phones. Many employees use popular consumer-level IM applications, such as AOL Instant Messenger and Yahoo Messenger. But some companies have opted to buy more secure, customized systems that offer such features as archiving.

Roughly one-third of U.S. employees use instant messaging at work, many without the knowledge of their employers, according to a 2006 survey by the American Management Association and the ePolicy Institute. Many employers remain reluctant to endorse it officially, fearing security breaches and distracted employees. But tech consultant Gartner Inc. projects that instant messaging will be the "de facto tool for voice, video and text chat" for 95 percent of employees in big companies within five years.

Unlike e-mail, instant messaging offers "presence" — a snapshot of which colleagues are available at a given moment. Together with allied Internet technologies such as blogs and wikis, it is "changing the way people collaborate," says Andrew McAfee, an associate professor at Harvard Business School. Companies "increasingly react to situations and problems on the fly, not solely by hierarchy," he says.

Instant messaging can "scare managers who were taught they need to be in control," says Marty Anderson, a professor at the Olin Graduate School of Business at Babson College. But others embrace the technology.

Suzanne Gordon, chief information officer for software maker SAS Institute Inc., Cary, N.C., "chats" daily via instant message with overseas staffers two or three rungs below her on the organizational chart. During one such session, a manager in France pointed out a flaw in technology support. Canvassing other employees by instant message, Gordon concluded the problem was serious enough for her to appoint a U.S.-based manager to help. "Sometimes through proper channels you don't always get the truth," she says.