Mike Tyson's pediatrician wife of four years filed for divorce Thursday in Montgomery County Circuit Court, alleging in court papers that the former heavyweight champion cheated on her.

Monica Turner, a doctor in her second year of pediatric residency at Georgetown University Medical Center, alleged in the divorce complaint that Tyson "committed adultery during the marriage, and such adultery has neither been forgiven nor condoned by the Plaintiff."

The boxer counter-filed his own divorce complaint Thursday in Las Vegas, his attorney said. "The basis is that the parties are presently incompatible," said Tyson's attorney James Jimmerson. "We don't have a fault-based statute where people are slinging mud."

Turner's attorney, Sanford Ain, would not discuss the alleged philandering. "We have every hope and expectation that the parties will reach an amicable resolution of their differences and hope there will be a settlement," he said. "I'm certain both parties are very much concerned about the welfare of their children and insulating them from this as much as possible."

Turner, 35, lives with the couple's two children, Rayna, 5, and Amir, 4, in a gated $2 million home in Bethesda overlooking Congressional Country Club. She and Tyson, 35, were married there in a quiet Muslim ceremony in April 1997.

"I saw two people who had great love and respect for each other," Muhammad Siddeeq, the Indianapolis imam who performed the ceremony, said yesterday. "I hope they find a way to work through this."

Siddeeq met the couple when he was overseeing Tyson's conversion to Islam while the boxer was serving a rape sentence at an Indiana jail from 1992 to 1995; he was convicted of raping an 18-year-old beauty pageant contestant in 1991.

Turner had caught Tyson's eye long before -- in 1990 at a party at comedian Eddie Murphy's house. She was from Washington's Petworth area, the half sister of Michael Steele, now chairman of the Maryland Republican Party. In the '80s, she had had a daughter with a convicted drug dealer 28 years older than she was; the child resides with Turner.

After she and Tyson met, they stayed in touch. After his incarceration, she flew to Indianapolis almost every two weeks to visit him in jail.

During their marriage the couple lived a relatively private life in Bethesda and took pains to portray Tyson as a devoted father, even as his legal troubles continued to mount. He was pictured kissing then-infant son Amir for the Father's Day edition of Esquire magazine in 1999 -- a photograph taken in the Montgomery County Detention Center while he was serving a one-year sentence for assaulting two motorists.

"With our kids, he's very involved," Turner told The Washington Post that year. "He's real protective of them. He always wants to make sure everything is right and that they're okay and they're happy."

But in recent months, rumors of the couple's estrangement have been swirling through the boxing communities in Washington and Las Vegas. Jimmerson said yesterday that for more than a year, Tyson has been living at his $3 million Las Vegas estate, located in a ranch community that's home to several celebrities, including singer Wayne Newton.

Jimmerson declined to discuss the mystery woman, or women, alleged in Turner's divorce complaint. "I regret that there would be this type of mud-throwing," he said.

In September, a woman told Las Vegas police that Tyson had raped her at his ranch, according to Lt. Jeff Carlson of the Las Vegas Metropolitan Police Department. The police concluded a four-month investigation into the accusation this week and forwarded the results to the district attorney's office yesterday, said Carlson. Police are recommending "that the district attorney pursue" the matter, he said. "We feel that there will be probable cause to substantiate the charge of sexual assault."

Ain would not discuss that investigation.

He said the couple discussed a divorce settlement, but no agreement had been reached. Turner is expected to retain legal custody of the children, he said. He declined to estimate Tyson's net worth. The boxer has extensive business interests and real estate holdings, in addition to the Las Vegas estate, and routinely pulls in multimillion-dollar purses for his prize fights.

A news conference has been scheduled for Tuesday in New York to announce Tyson's next fight -- a long-awaited match with reigning heavyweight champion Lennox Lewis -- tentatively scheduled for April 6. Although no site has been set, industry sources expect the fight to gross more than $150 million, making it the most lucrative in the sport's history.

Turner's divorce complaint alleges that her $17,000 annual income from her second year of residency is not enough to meet the standard of living she became used to during their four-year marriage. Tyson's complaint, filed in Clark County District Court in Nevada, counters that both he and Turner are self-supporting, and "neither party is entitled to an award of support and/or alimony each from the other."

Friends of the couple expressed hope yesterday that the divorce would not be a repeat of the bruising public spectacle that surrounded Tyson's 1988 split from actress Robin Givens after an eight-month marriage.

"They're human and they should be allowed to live as humans and try to work through whatever their concerns are," Siddeeq said. "I'm sure they'll do that."

Unlike Givens -- who, in a now-famous interview with Barbara Walters, accused Tyson of being a violent manic-depressive -- Turner has declined to discuss her marital woes publicly. "She's very dignified, highly principled," Siddeeq said.

And Tyson, though still prone to erratic behavior, may have changed, too, suggested one lawyer who has had dealings with him.

"The Mike Tyson of today is not the Mike Tyson he was back then," said celebrity lawyer Raoul Felder, who represented Givens in her divorce. "He's an older man, and you get mellower with age. His wife is a special person, a physician. I expect they're going to have a very civilized divorce."

Staff writer Micah Pollack and researcher Bobbye Pratt contributed to this report.

Mike Tyson and Monica Turner in 1998. He has been living in Las Vegas, she in Bethesda.Monica Turner and Mike Tyson in 1998. Both filed for divorce on Thursday after four years of marriage.