More than a third of 815 consecutive patients admitted to a Boston University Medical Center medical ward developed an illness or disability caused in some way by their hospitalization. Sixteen died.

Thirty-six, or one-half of 1 percent, of 5,612 surgical patients admitted to Boston's Peter Bent Brigham Hospital -- a famed Harvard affiliate -- suffered an "adverse outcome" caused by some kind of surgical error. Eleven died, and five were left with "serious physical impairment."

In 1979 in California, 30 hospitals did risky open-heart surgery on children, but only three -- by most standards -- did enough such operations to make sure of safety and best possible outcome.

These three revelations are made in three articles in the most recent New England Journal of Medicine. All describe conditions many authorities consider typical throughout the country in large hospitals and small, though few doctors talk of them publicly.

Twenty-three of the 36 unfortunate surgical patients at Peter Bent Brigham actually were admitted after unwise or botched operations at other hospitals.

Most of the Boston University hospital mishaps were probably unavoidable. Many were adverse drug reactions in severely ill, often older patients who needed the drugs. There were also many complications after complex diagnoses or treatments, like cardiac catherization (threading a catheter through the heart) or intravenous therapy.

But between 1 and 5 percent of the Boston University mishaps -- different percentages in different kinds of patients -- were clearly "easily preventable," an experienced hospital analyst commented after reading the Boston University article.

"We're talking about things that happen all through medicine," said Dr. Francis Moore, a noted surgeon and Harvard professor emeritus who co-authored the Peter Brent Brigham article.

In surgery, he said, "these things are infrequent, but they are fantastically expensive. They are expensive in terms of human life and suffering and also in dollars. It cost $1.7 million to care for these 36 patients."

Peter Bent Brigham hospital was named in the article by four of its staff.

The Boston University center was called only "a large university teaching hospital," but Boston sources said it was indeed Boston University.

"I think this hospital has good quality of care," said Dr. Paul Gertman, a co-author of the Boston University study. "The real point is that we don't really know how many of these things are correctable."

They are happening more often, however, all the authors agreed. This is partly because there are more older, vulnerable patients, partly because care has become more complex and technological, with more potential for both life-saving and harm.

"The important thing," Gertman said, "is that there should be a major effort everyplace to find out how much correctable error there is, then correct it."