Your boss asks you to step into his office. You know he's upset with your recent work, and he's going to tell you about it.

How will you handle the criticism?

You're the boss, and one of your subordinates has been showing up late for work for the past couple of months. You've put off saying anything, hoping the person would shape up.

You find it difficult to criticize; is there a way to avoid hard feelings on either side?

This time it's the boss who has blundered. Somebody has to speak up and tell him he's making a mistake.

Are you putting your job in jeopardy?

Criticism -- whether giving it or taking it -- is unavoidable. Sometimes it can wreak havoc in an office, where an angry boss humiliates a worker, or the employe becomes over-defensive.

Or, says Lawrence D. Schwimmer, a former Chicago business executive, it "can be an opportunity for learning.

"Criticism is the true test of a professional," says Schwimmer, who now offers assertiveness seminars around the country. "Real pros know how to handle it and grow from it.

"One of the best ways to become a success at what you do," he writes in a new book, "How To Ask for a Raise Without Getting Fired -- And 24 Other Assertiveness Techniques for the Office" (Harper and Row, 176 pages, $3.95 paper)," is to maximize your ability to give and receive criticism while minimizing your natural defensive reactions.

"Raised hackles and a raised voice are almost never the proper response to criticism -- no matter how unjust."

Before he was 30, Schwimmer, now 34, turned his small prepackaged-sandwich firm into a multimillion-dollar business. Later he became a marketing executive for Planters Peanuts. He formed his seminar firm in 1977: "I was a capable, successful businessman in the body of a natural teacher and trainer. I felt working with profits and products wasn't as satisfying as working with people."

His seminars, he says, draw a large percentage of men who "want to learn how to deal with hostile, hard-to-get-along-with executives that they have to get along with" to get promoted.

In the workplace, whether you're the clerk or the chief, says Schwinner, you are probably using one of three "basic communications styles: assertive, aggressive or nonassertive."

Assertive , "means communicating honestly and openly." You "support yourself and your rights without riding roughshod over others' rights."

Aggressive communication "is intended to dominate and himiliate."

Nonassertive : "passive submission to others' wants and needs" -- at your expense.

Criticism, says Schwimmer, "is an important tool of the assertive approach" -- in which you "take 100 percent responsibility for your own life by expressing your thoughts" and "standing up to conflict."

One of the first things you can do to make it easier to handle criticism, he advises, is to recognize your faults, and then make use of that self-knowledge.

If you tend to be sloppy with figures, and mathematical errors keep appearing to embarrass you, find a co-worker who will "read the numbers as a final check."

If you are aware of areas in which you are weak, then you won't be "shocked and hurt -- nor defensive -- when you are justifiably criticized. It may even motivate you to change."

When the boss is pointing out the errors of an employe's ways, typically, says Schwimmer, the employe responds "apologetically, defensively or in an attacking manner." Instead, consider these alternatives:

Accept -- if the criticism "is basically true and realistic." And don't apologize. An employe who apologizes for mistakes can appear insincere if he or she can't manage to correct them.

Disagree -- if you think you've been wronged. Often, says Schwimmer, the nonassertive person will feel, "Oh, what's the use, the boss thinks. . . "

Sometimes a boss may make a broad assertion, such as: It's 10 minutes after 9. Don't you ever start work on time?" In a case like this, "focus on the point that isn't true" by telling the supervisor: "Today is an exception. Normally, I'm in my office by 9."

Your supervisor may be guilty of a criticism based on faulty value judgment. Schwimmer recalls the story of one woman who turned down her boss' request to work late because her husband was home ill.

A few weeks later, during a salary review, the boss told the woman: "I don't like your attitude. You're not committed."

Taking the assertive approach, she spoke up and countered: "I've worked overtime every other time you've asked. That's about 30 times."

She would have made a mistake by keeping quiet or by getting aggressively angry and perhaps remarking: "So this is what I get for all my work."

Set limits . Bosses sometimes can be especially aggressive or hostile in their criticism, "and people don't know how to handle it." If a boss makes an angry statement, such as "This is the stupidest thing . . . " you might reply: "I may lack experience, but I don't lack intellect."

Delay . If a criticism catches you by surprise -- and particularly if "the boss is foaming at the mouth" -- give yourself some thinking, and cooling-off time. Say: "Excuse me, but I don't know how to respond to that. Let me get back to you in 30 minutes."

People do make mistakes. The assertive ones, says Schwimmer, "count as one of their professional rights the right to make mistakes. So they tend to value a coworker who brings mistakes and oversights to their attention."

If your are the boss, and you find it necessary to correct an errant subordinate, Schwimmer suggests you:

Avoid hostility . Put the emphasis on "changing and improving the other person's behavior." Your attitude should be: "I like you, but I don't like what you are doing."

Use "I" versue "You" language . It is a "classic mistake" to begin: "You were wrong." It makes the employe "defensive." Rather, begin: "I'd like to talk to you about your report."

Another example: Don't say, "You can't be serious about your proposal." Make it, "I can't agree with your proposal. I have another idea." As a manager, he says, you have to be "a mini-psycholist."

Don't apologize for your criticism . "You only weaken it."

Don't resort to conning tactics . "Don't give three positives" to employes" and then blast them."

Do it privately .

You need to be able to criticize constructively, says Schwimmer, to climb the leadership ladder. Being able to criticize "gets the results you need -- better performances from your coworkers and subordinates."

Bosses need criticizing, too, says Schwimmer, and if they know what's good for them they'll reward -- not punish -- a staff member who speaks up.

Once, when he was about to make a report at a "high-level" departmental meeting, a staff newcomer pointed out some statistical errors that had led him to invalid conclusions.

"I owed that assistant a real debt of gratitude for having the courage to speak up."

Smart managers, he says, "encourage assertiveness. There's no value in 'yes men.' You get robbed of their brain power."

The assertive approach to the workplace, says Schwimmer, "is not meant as a guarantee. But it does maximize your chances to start up" the career ranks "and to get what you want without offending others."