Mark Willes fired himself yesterday as publisher of the Los Angeles Times.

Willes--who will keep his day job as chairman of Times Mirror Co.--replaced himself after a controversial 21-month tenure that sparked fears he was tearing down the wall between the business operation and the newsroom. He named Kathryn Downing, the newspaper's president and chief executive officer, as the new publisher.

"Good leaders know when to get in, and they also know when to get out. . . . It's now time for me to get out of the way," he told reporters.

Willes ordered advertising executives to work with section editors to boost revenue at the Times, saying he wanted to "blow up" the existing structure. This caused journalistic concerns that advertisers might try to use their economic clout to influence coverage. Such concerns turned out to be largely unfounded.

A former General Mills executive, Willes was dubbed the "Cereal Killer" after closing the widely respected New York City edition of Newsday, a Times Mirror paper. He also stirred controversy last year by saying that female readers are drawn to stories that are emotional, not analytical. He said yesterday he understood the concerns about his publisher's role "because I was new and I had no track record in journalism. I think that issue has fundamentally gone away because people realized I didn't interfere in an inappropriate way . . .

"I put myself in to both accelerate the pace with which we could make that change and because some of the ideas we had were quite radical by newspaper standards . . . I wanted to make sure there was nobody else to blame if they didn't work." He said his decision to step down--which came as a surprise--was "exceptionally painful."

Circulation, now 1.1 million, has increased during Willes' tenure, but earnings have declined for five straight quarters, though he said he would report increased profits for the quarter ending this month. Willes said he has tried to "reinvent" the Times but that "it has been a very difficult period." Downing said she hopes to add another million readers but would not say how quickly such a startling increase might come about.