THIS WEEK the National Institute on Drug Abuse published the results of a federal survey on drug use, which President Bush hailed as "wonderful" news. Before that message could be absorbed, though, critics of the survey and some Hill Democrats assailed the report as misleading and too optimistic. Sen. Joseph Biden (D-Del.), chairman of the Senate Judiciary Committee, immediately released another study based on drug tests given to those arrested in major cities. These figures, Sen. Biden says, are not at all encouraging.

Both reports are replete with numbers, charts and head counts that purport to tell the public how many people use what kind of drug and how often. Both offer statistics that are extrapolations from samples. We think Sen. Biden makes a good case that the NIDA survey, based on questionnaires and interviews with householders, is overly optimistic, since it did not include whole populations -- college students, hospital or treatment center patients, prison inmates and the homeless, for example -- that are likely to include large numbers of drug users. The survey also depends on the honesty of citizens in discussing their illegal drug use with government representatives. But even accepting the higher Biden figures, the news is not all bad. True, there continues to be a sizable hard-core population of drug addicts and frequent users who are also responsible for the rising number of violent crimes such as murder and robbery. But everyone agrees that drug use in the population as a whole is continuing to decline sharply.

In 1985, for example, NIDA estimated that 5.8 million Americans used cocaine once a month; that figure has now fallen to 1.6 million. Tobacco and alcohol use has also dropped dramatically in the same period. Sen. Biden may dispute specific figures, but he agrees that "casual drug use is down, {and} the nation's attitudes are turning against drugs." The message of both reports, we believe, is that education is working to deter drug use and other substance abuse in a large part of the population, and that is worth celebrating. But it would be a mistake to ignore the continuing problem of hard-core users, who are not only self-destructive but often dangerous in the community. Here, Sen. Biden's advice -- to err on the side of pessimism and prepare, in terms of treatment facilities, police, prison facilities and medical research, for the worst -- is well taken.