Workplace communications have been speeding up for years, and they appear to have finally reached a terminal speed. Can you get any faster than instant messaging?

Sean Jazayeri calls instant messaging "a godsend." "I can find out if my CEO or CTO is online. I can make decisions or get approvals on the fly and get things done," says the chief information officer of Avanade Inc., a Seattle technology-integration company that helps other companies use Microsoft products.

Sometimes Mr. Jazayeri sends instant messages to the company's director of infrastructure who can field the messages on his mobile phone while riding the bus to work; he can also reach its chief technology officer who picks up the messages on his watch.

Yet even Mr. Jazayeri has reservations about the ability to have instant access to colleagues. "I would say that at least half the IMs I get I'm always thinking, 'Why did you use IM for this?' " he says. "To me, it's kind of like opening someone's door and barging in and asking them a question."

Mr. Jazayeri's experience neatly sums up the biggest pros and cons of instant messaging, which is similar to e-mail but pops up on a computer screen, demanding immediate attention. Yet for many workers there will be no turning back from the technology, because its use is exploding in the workplace.

Tens of millions of employees currently use instant messaging. About 75% of companies surveyed by Gartner Inc., an information-technology research firm based in Stamford, Conn., report that employees use instant messaging at work. In about a third of those cases, workers are using instant messaging sanctioned or managed by their company. The trend is growing fast. "E-mail is going to shrink in scope as IM and other collaboration tools begin to take back areas where e-mail has expanded," says Lou Latham, a principal analyst with Gartner.

At companies like International Business Machines Corp., which provides instant-messaging software called Lotus Instant Messaging to 11 million business users, the tool has become second nature as a way to communicate among co-workers. The company's 300,000 employees send between three million and five million instant messages a day. "It changes your responsiveness and also your expectations of how quickly the company works," says Ken Bisconti, vice president of collaboration products. He says the technology helps reduce travel and long-distance phone tag.

Instant access to information also can give a company an edge over companies relying on slower means of communicating. At Shaw Pittman, a law firm in Washington, D.C., instant messaging has contributed to the demise of a roomful of fax machines. Instead of relying on constantly churning fax machines, lawyers rely far more on instant messaging. "There are times when you want to get a message to someone that needs to be quicker than e-mail," says Jim Alberg, a partner and chair of the firm's technology practice.

Yet as with e-mail, there are dangers associated with instant messaging. Inappropriate use of the messaging technology in the workplace can even lead to termination just as it can with e-mail.

Here are some tips to remember when using instant messaging in the workplace.

Keep instant messages, as well as e-mails and other office communications, to business matters. You can set your instant messaging to let your friends know that even though you may be online you're busy. In general, it's a good idea to filter out friends while you're at work. Also, be clear about what kinds of messages really need to be sent instantly, since misusing the technology can telegraph to co-workers that you don't know how to effectively prioritize projects.

Being overly casual with colleagues and superiors is one of the biggest pitfalls of using instant messaging. "We all get drawn into using instant messaging and it's as if we're having a private conversation with a friend," says Lori Davila, an Atlanta career coach and author of "How to Choose the Right Person for the Right Job Every Time." It's important to follow the lead of managers but not get lulled into overfamiliarity, she says, adding, "Choose your words wisely, because Corporate America is definitely watching."

In fact, many companies do keep logs of instant messages. Just because instant messages vanish from a computer screen doesn't mean they aren't being saved somewhere. The National Association of Securities Dealers requires securities firms to both record and monitor all instant-message conversations. But other firms do as well, in some cases without informing employees. Infractions can range from a slap on the wrist to immediate dismissal.

"What is sometimes overlooked by users of instant-message software in the securities industry is the simple fact that not only is the firm they work for logging the messages, but it is just as likely that the firm of the counterparty they are talking to in the IM is also recording the messages," says Robert T. DeMarco, CEO of IP Group, a Delray Beach, Fla., instant-messaging software provider.

If anything, instant messaging seems to increase the odds of embarrassing gaffes, because the messages are sent so rapidly. Sometimes it's also important simply to remember to turn off instant messaging.

Mr. Jazayeri recalls a time when he borrowed a laptop from a staffer to make a slide presentation. When the colleague noticed that her instant messaging was still active, she grew increasingly anxious that her boyfriend would send an embarrassing message that would be projected for everyone to see.

"She asked me, 'Would you fire me if an IM came through?' " recalls Mr. Jazayeri. "I said, 'No, I would have just laughed.' "