It's hard to pinpoint how it started. Maybe it was when you saw your manager's assistant noting those rare occasions when you came in 10 minutes late. Or maybe it was the time the boss half-jokingly trashed your performance -- in front of her higher-up.

There now seems no end to your tormentor's campaign of psychological harassment and personal and professional destruction -- aimed squarely at you. The nitpicking, the demeaning comments, the misleading digs and full-blown lies have all come together to exact their intended effect: to make you quit or get fired.

This is the ugly picture of bullying in the American workplace, painted by workers who describe themselves as targets and by the professionals who advocate for them. "My supervisor would take my case files to inspect them, and then write me up at the end of the day because the files weren't complete," says a former employee of a California social-service nonprofit. "He undermined me all around, which is not what a good supervisor does."

According to The Workplace Bullying & Trauma Institute Web site, telltale signs you're being bullied at work manifest themselves both in and outside the office. Just a few include apprehension about going to work and agitation and anxiety while you're there, surprise, agenda-less meetings where you're humiliated, never being left alone to do your job, and false accusations of incompetence.

The essence of workplace bullying is to twist political and social power to inflict psychological abuse on a carefully chosen target. But the vast majority of such incidents are not illegal in the US, according to Gary Namie, PhD, president of The Workplace Bullying & Trauma Institute in Bellingham, Washington, and author of The Bully at Work.

One in six American workers experiences workplace bullying, Namie says, and most bullies and their targets are women. However, 42 percent of the perpetrators are men. Employers and workers can both play roles to prevent or stop bullying, which can destroy careers and lives.

Companies should be concerned about bullying, if for no other reason than its potential to damage the bottom line. "Employers are frustrated with turnover and disruption caused by bullies," Namie says. It often costs a company tens of thousands of dollars to recruit, hire and train a new employee to replace a bullied worker who left.

What should companies do to prevent psychological abuse among workers? As with any form of harassment, management's vigilance is key.

"The employer should be close enough to day-to-day activity to recognize and appropriately inquire about intimidation going on," says Craig Pratt, an HR consultant and coauthor of Investigating Workplace Harassment: How to Be Fair, Thorough, and Legal.

But such awareness won't necessarily end bullying. "Even in the best of circumstances, there will be people who behave badly," says Kim Vosburg, director of human resources for Gene B. Glick Co., an Indianapolis property-management firm. "The senior HR manager must let the bully know that that behavior will not be tolerated, period."

But be aware that employers are out to protect themselves. Often, their chief legal concern is avoiding any backlash that could result from taking action against an employee accused of bullying, says Karen Karr, special counsel at Steptoe & Johnson LLP in Phoenix. "If some harm does come to the bullied person and the employer could have prevented it, there's some liability, generally covered by workers' comp," she explains.

It's easy to say that targets should respond aggressively to bullies, but it's not always possible. "A lot of people who are targeted can't fight back," Namie says. "They don't have it in them."

The alternative is to involve human resources, a higher manager or an outside advocate, such as a consultant or lawyer. But don't confide in anyone close to the bully -- that could make matters worse. And make sure you document the abuse.

If you're being bullied, leaving your job is sometimes the only way to salvage your physical and mental health. "My boss was killing me -- destroying my health," says a technical writer bullied out of her job. "I had three heart attacks during that time."

If you leave, tell the powers that be why. "The nature of the departure is what predicts your health," Namie explains. Bullied workers who go out fighting are likely to get past the nightmare relatively quickly and move on to a better work situation. "If you skulk away in silence, the bully gets to be the oral historian," he says.

Part 2: Workplace Bullying: Who's Your Bully?