Drinking caffeinated coffee does not appear to increase the risk of heart disease or stroke among men, according to a research report to be published in today's New England Journal of Medicine.

The findings, the latest in a series of conflicting reports about risks of coffee consumption, appeared to rebut those of earlier, smaller studies that suggested drinking five cups of coffee a day might increase the risk of coronary heart disease twofold or threefold.

The only warning sounded by the researchers, who studied 45,000 men, was for individuals who drink more than four cups of decaffeinated coffee a day -- a consumption pattern that they said correlated with a marginally significant risk of heart disease. But the study's authors said the number of decaffeinated-coffee drinkers they surveyed was probably too small to allow them to draw definite conclusions about hazards.

"We can't exclude the possibility that there may be some risk associated with coffee," said Walter Willet, a researcher at the Harvard School of Public Health who led the study. "But even if there is, it is not a major public health issue. . . . The main message here is that for people drinking up to six cups a day, there is no strong reason to give up coffee and, particularly, no strong reason to switch to decaf." Willet's study focused only on men, but he said he would be surprised if women responded differently to coffee. A second study, focusing on women, will be completed next year.

Other health experts, citing the number and variety of conclusions drawn from coffee studies over the years and the complexity of caffeine's effects, said that the Harvard group's findings should not be taken as the final word on relative risks of coffee drinking.

"Perhaps if we had some better insight about what it is in coffee that might lead to risk, we might be able to close the book on this issue. But we don't," said Gary Friedman, an epidemiologist at the Kaiser Permanente Medical Center in Oakland, who is coauthor of a major coffee study released this fall. "I don't think we really understand what is going on with {coffee}. The public wants a clear-cut answer. But we can't give it to them yet."

For years, researchers have examined possible risks to the cardiovascular system of coffee consumption because caffeine stimulates heart rates and, in some cases, raises blood pressure and cholesterol levels.

But teasing out the precise impact of caffeine on heart disease has been difficult because the risk -- if it does exist -- is thought to be very small and studies, therefore, contain large margins of error. In addition, many people who consume large amounts of coffee also engage in other behavior, such as smoking, that may carry high risks of heart disease. Separating the effects of caffeine from those of other factors, such as tobacco, has been difficult.

A 1986 study, for example, showed that those drinking more than five cups a day had a heart disease risk three times greater than that of people who drank no coffee. But the study involved only 1,100 people, a number viewed by some researchers as too small to generate consistent, dependable results.

The Harvard study found that the risk of cardiovascular disease among those who drank more than four cups of coffee daily was about 4 percent greater than that among people who drank no coffee.

Men who drank only caffeinated coffee were found to have no increased risk of cardiovascular disease at any level of consumption. The only substantial increase in risk was observed among men who drank four or more cups of decaffeinated coffee daily.

The study's results were described as largely in line with those of another recent coffee study conducted by Kaiser Permanente. Although that research showed a 40 percent increase in the risk of heart disease for those who drank more than four cups of coffee a day, both Kaiser and Harvard researchers said that, after the large margin of error involved in estimating coffee-related risks of heart disease was taken into account, the two studies were largely in agreement that risks associated with coffee were small.