Kenneth William Clark, who as a 15-year-old murdered his mother, brother and two sisters in their Rockville home in 1969, was released this week from a Maryland mental institution after nearly 11 years of psychiatric treatment.

Clark walked out of a Montgomery County courtroom on Monday after psychiatrists declared that he is no longer a danger to society.

"Now I have a chance to make a new life for myself and to prove myself," his lawyer quoted Clark as saying as they left the court.

Clark plans to live in Baltimore andbegin training as a chef next September, according to a psychologist at Clifton T. Perkins Hospital, the maximum-security facility in Jessup where Clark received most of his treatment. He must continue to live in Maryland and see his therapist once a week, under terms of the "conditional release" granted this week by Circuit Court Judge Joseph M. Mathias.

In the early morning hours of Jan. 25, 1969, Clark massacred four members of his family -- three with a hatchet, one by strangling. He had just awakened from a recurring nightmare in which he dreamed that his younger brother was threatening him with a candle that turned into a club studded with blades, according to testimony at his trial.

Clark's father, a Navy lieutenant who was in Vietnam at the time of the killings, was the only member of the family spared. The father visited Clark a few times at Perkins, but Clark has not seen him since the mid-1970s.

Psychiatrists testified that Clark was a "chronic schizophrenic," and the youth was found not guilty by reason of insanity. He was admitted to Perkins Hospital on May 29, 1969.

Clark spent the next 11 years in and out of Perkins and another state hospital -- a period marked by two escapes, two suicide attempts, a marriage and its breakup and several failed efforts at living and working outside the institutions.

But Perkins' psychologist, Leonard Ainsworth, said yesterday that "it has been a long time" since Clark has shown any "schizophrenic symptoms," and that Clark "should do well outside" as long as his past life does not interfere. The major risk, the psychologist said, is suicide.

"He will always feel guilty," said Ainsworth. "I think he'll always be a suicide risk because of the guilt, the guilt he has to live with the rest of his life. He's acutely aware of that."

Indeed, in an interview in September 1978 at Springfield State Hospital in Sykesville, Md., where he had been transferred as a first step toward release, the tall, boyish-looking Clark described his suicide attempts and the reasons behind them.

The first time he took pills, but was found unconscious and hospitalized, he said.The second time he tried to kill himself with carbon monoxide poisioning in his car, but the car stalled.

There was "a need to pay, a desire to give up, to kill myself so I wouldn't have to deal with it anymore," said Clark, who refers the murder of his family as "the tragedy."

Of that January night in his Rockville home, Clark said, "I was sick. . . . But when you get well, how do you deal with it? I can remember it in the minutest detail . . . but because I was crazy doesn't mitigate it."

"For years, I wore my heart on my sleeve," Clark said. "I felt I had to give my heart and soul away to get approval, to be thought of as a nice guy."

But Clark said that after his second suicide attempt in 1977 and another year of treatment at Perkins, he realized he "would have to learn to live with it -- deal with it."

Clark said if he killed himself "it would make all the time, the care, the money my family put into raising me up to 1969 meaningless. It would make even the tragedy that put me in Perkins meaningless."

Clark said plaintively: "I can't undo it. Nobody can. Keeping me locked up in a nuthouse won't do it. Neither will suicide."

After his 1969 trial, where he was portrayed through testimony and records as a troubled, brilliant and stubborn youth who had previously been involved in incidents of stealing, drinking and cruelty to animals, Clark spent four year at Perkins. In 1973, he was placed on conditional release. While living in a halfway house, he married, but later attempted suicide and was returned to the hospital.

In 1975, he was granted permission to attend college classed, but eluded a hospital guard who had taken him to a University of Maryland campus to enroll. He fled to Ohio and then Kentucky. Later that year, after working at various jobs, he was arrested in Hopkinsville, Ky., and returned to Perkins.

In the summer of 1978 Clark was sent to Springfield Hospital after Perkins psychiatrists reported that he was improving and recommended that he be moved to a "more open setting." In February, 1979, he disappeared while commuting to a Baltimore job as a busboy.

FBI agents apprehended him in Van Nuys, Calif., last June, where he was working under his own name. He was brought back to Maryland and to Perkins.

Under the provisions of conditional release, Judge Mathias will retain authority over Clark for an indefinite period. Clark must remain in the state, adhere to a schedule of visits set up by his therapist, participate in a job training program, and refrain from the use of alcohol and illegal drugs. He also is prohibited from owning a handgun.

If Clark breaks any conditions of his release he can be brought back to court and recommitted.

Clark's lawyer, Alan Katzen, said that "after 11 years of diligent treatment, this man is no longer insane. Of course the guy still has problems, but anybody confined to a facility that long would have problems. His biggest problem is adjusting to society after 11 years, but that's just what he's going to do."