Stu Kerr, the pioneering television host whose many roles became fond memories for generations of Baltimore children, died early yesterday at his Riderwood home after an eight-year battle with bone marrow cancer. He was 66.

His four-decade career in broadcasting coincided with the rise of television, and no face or name was more closely associated with the medium in Baltimore. He is best remembered for his folksy, imaginative performances as Bozo the Clown, the zany Professor Kool, the conductor of "Caboose," Mr. Fortune of "Dialing for Dollars" and Commander Stukker of "54 Space Corps."

At WMAR-TV (Channel 2), which he joined in 1952 after serving in combat in Korea, he was the jack-of-all-trades, working as weatherman, lottery host and chief announcer, as well as writing and performing in his own shows. He was also a frequent guest on "Captain Kangaroo," where he played a scatterbrained newsman called Mr. Scoop Toot.

Though he never lost the taste for quiet times at home with his family, Mr. Kerr kept up a whirlwind schedule of public speeches and performances, both for charity and for pay. In the 1970s, he averaged 135 public appearances a year -- not enough to keep up with demand, which sometimes reached 250 requests a month.

After a bitter parting in 1981 from WMAR, where new managers believed his time had passed, Mr. Kerr was a weatherman for WJLA-TV (Channel 7) in Washington, performed "54 Space Corps" on WNUV-TV (Channel 54) in Baltimore and did commercials for Blue Cross-Blue Shield and other businesses.

"He was the most talented person I ever worked with," said Kevin Clash, a Baltimore puppeteer discovered by Mr. Kerr for "Caboose" who has gone on to perform characters on "Sesame Street" and "Dinosaurs" and other national shows and to win an Emmy Award.

"He wrote the scripts and acted all the parts. There was nothing he couldn't do," Mr. Clash said. "He was very underrated, though not by his Baltimore fans."

"You saw the same guy on TV that we saw at home," said Nancy Kerr of New York City, at 29 the youngest of Mr. Kerr's four children. "He was the funniest man I've ever known. Our house was filled with laughter all the time."

Thomas Stewart Kerr was born on March 9, 1928, the son of Scottish immigrants, in New York City. He was voted the shyest member of his class at Yonkers High School, but he was smitten in his teen-age years with a love of broadcasting that would never leave him.

He trained himself at home using a microphone jury-rigged to the living room radio until he got a job as a page at NBC in Rockefeller Center in Manhattan, "sitting in Lowell Thomas' seat right after he left, while it was still warm," he later recalled. There, he would salvage old radio scripts from the trash and practice reading them, or ask professional announcers to critique his rendering of popular commercials of the day.

His father, a janitor and carpenter, couldn't understand why a youngster with a chance to become a longshoreman would instead choose the newfangled world of radio. But at the age of 19, Mr. Kerr landed his first on-the-air job at WANN in Annapolis.

From WANN, he went on to brief stints at WFND in Frederick and WINX in Washington before being drafted into the Army. He served in the infantry in a heavy weapons company, seeing 270 days of combat in which a third of his unit's soldiers were killed or wounded.

From Korea, he returned to Baltimore in 1952 and found his first television job as night announcer at WMAR, then in the old Sunpapers building at Charles and Redwood streets. The station management decided there was an audience for a show later than the 11:30 p.m. sign-off and directed Mr. Kerr to come up with something.

He invented "The Janitor," dressing in a dirty cap and tattered GI shirt and toting a mop and pail around the deserted studio and corridors, pursued by a single camera. He developed a talent for improvisation that would be remarked on by many who worked with him: complaining about cigarette butts, talking to a nonexistent boss and introducing short films.

When the station switched him to a morning slot, Mr. Kerr kept the character but renamed the show "The Early Riser," showing cartoons and lip-syncing to hit songs. With the advent of videotape, he experimented, pantomiming all four Beatles and having technicians combine the four Stu Kerrs on a single screen.

When WMAR moved to shiny new studios on York Road, Mr. Kerr decided to leave the shabby janitor behind. Though he doubted his ability to entertain children, he became Baltimore's Bozo the Clown, the local host in a franchised show that came with a collection of Bozo cartoons.

When the station's 150 Bozo cartoons wore out from overuse, managers asked Mr. Kerr to come up with a new children's show. He responded with the capped-and-gowned Professor Kool, who offered menus containing "Poison Ivy Pudding" and sent children to the school nurse for headaches, only to have them return with arms in slings.

"The things I learned, just listening to the kids," he recalled later. "If parents would do that, they'd learn a hell of a lot about their kid and how fascinating their minds are."

John Ziemann, a WMAR technician who played the villainous witch Miss Spider Web on the show, last night remembered Mr. Kerr's ability to cope with disasters.

"One day I missed my mark and came out the wrong door -- I was behind him instead of in front of him," Mr. Ziemann said. But Mr. Kerr turned the goof into an extended joke for the viewers, pretending not to suspect the witch was present, and "the kids ate it up," Mr. Ziemann recalled.

After Professor Kool, Mr. Kerr developed "Caboose" in 1978. But after a couple of years, it was shifted from its Saturday morning time slot to the afternoon, losing its audience in the process. Another Kerr staple, "Dialing for Dollars," a syndicated show that gave away $800,000 in Baltimore in its 38-year run, had left the air in 1977.

In a "realignment and restructuring" at WMAR in November 1981, Mr. Kerr was fired at the age of 53. His family yesterday recalled his dismissal as an unexpected and painful blow, though his reputation guaranteed him plenty of paid appearances on television and off.

In an interview a few years ago, Mr. Kerr expressed regret at the changing nature of family life and television's role in it. "When TV was first started," he said, "it was watched by the entire family. Now it's a lot of children, watching TV alone."

In addition to daughter Nancy, Mr. Kerr is survived by his wife of 38 years, the former Mary Elizabeth Thatcher; two other daughters, Cathy Gvozden of Severna Park and Barbie Murphy of Chesapeake, Va.; a son, Doug Kerr of Woodstock, Ga.; a brother, David Kerr of Desplaines, Ill.; a sister, Margaret Clark of Peekskill, N.Y.; and seven grandchildren.

A viewing is planned for Wednesday from 2 p.m. to 4 p.m. and 7 p.m. to 9 p.m. at the Ruck Towson Funeral Home, 1050 York Road in Towson, where the funeral will be held at 10 a.m. Thursday.

The family suggests memorial contributions to the Union Memorial Hospital Hospice, the John McGovern Oncology Support System at Greater Baltimore Medical Center or any local charity.