The editor in chief of the prestigious New England Journal of Medicine will step down from his post later this year because of a dispute with his employer over the extent to which the journal's name should be used to endorse publications, sources said yesterday.

The move is the second high-profile departure of a medical journal editor this year and the second controversy over product endorsements by a prominent medical society in the past two years.

People familiar with the latest episode said it's indicative of new financial pressures being brought to bear on medical organizations--and in particular on medical publishing companies, which are feeling threatened by the emergence of electronic on-line publications. Jerome P. Kassirer, who has overseen the 187-year-old weekly for eight years, will begin a seven-month sabbatical Sept. 1 and will formally step down from his post March 31, when his contract expires, Kassirer said yesterday.

The outgoing editor declined to go into details about why he was leaving. A joint statement released by him yesterday with Jack T. Evjy, president of the Massachusetts Medical Society, which owns and publishes the journal, said there had been "honest differences of opinion between Dr. Kassirer and the Medical Society over administrative and publishing issues."

But sources familiar with the controversy said the sole issue was whether the medical society would expand its limited use of the journal's valuable imprimatur for various publications or medical educational products.

Kassirer has long opposed lending or selling the journal's highly respected name to any product that does not adhere to the same editing standards to which the journal holds itself. Observers said that standard is a tough one to match for consumer-oriented publications, which simplify new research findings for readers more interested in take-home messages than in scientific details.

A few non-research publications owned by the medical society already bear the inscription "From the publisher of the New England Journal of Medicine," using the journal's familiar typeface and logo. Insiders said the medical society wants to use that promotional tactic more, along with other so-called co-branding ventures. One option considered (and ultimately dropped), for example, would have created an Internet link between the journal's on-line book reviews and Barnes and Noble's on-line bookselling business, said Frank Fortin, the medical society's communications director.

Kassirer's departure is reminiscent of the January ouster of George Lundberg as editor of the Journal of the American Medical Association, but the issues are quite different, Kassirer and others said. The American Medical Association fired Lundberg 17 years into his editorial stint for publishing research about oral sex during President Clinton's impeachment trial. The research concluded that only 40 percent of college students would say they'd "had sex" if their sexual activity were limited to oral sex--a finding some saw as an attempt to defend Clinton.

By contrast, Kassirer said yesterday, he has long enjoyed full editorial independence. The problem, others said, was with how the society would market the journal and its name. In that respect, the controversy more closely resembles the American Medical Association's abortive 1997 effort to lend its name to products made by Sunbeam Corp. That deal, seen by many as a corporate sell-out, was quickly reversed by the AMA's membership and led to several high-level resignations and a lawsuit from Sunbeam that cost the AMA $9.9 million.

Fortin said the medical society was interested in using the journal's name only to endorse medically related publications. He declined to reveal any projections of how much the society might profit from wider use of the journal's name.

Several doctors on the journal's editorial staff said the society had spent large amounts of money lately, including an undisclosed sum for an elegant new headquarters building in Waltham. (The building consolidates several far-flung society offices, Fortin said, and includes a much needed conference center for the society's many medical education programs.)

Some journal editors also said the society was feeling financially threatened by the recent growth in on-line publishing, and in particular by a recent proposal by National Institutes of Health Director Harold Varmus to launch a free science journal on the World Wide Web.