FOR YEARS environmental groups have been trying to strengthen federal regulation of pesticides. Makers and users of the products -- chemical companies and farm groups -- have blocked them. Now 41 of the nation's leading environmental groups have reached an extraordinary agreement with 92 of the largest chemical companies on a set of amendments to existing law.

Farm groups and some manufacturers continue to have reservations, and the Environmental Protection Agency says the timetables in the amendments are unrealistic. But hearings have been promised in both House and Senate Agriculture committees; the amendments can themselves be amended if there is a need. The problem is serious, and the agreement between these traditional adversaries presents both an opportunity and test of good sense and good faith on all sides.

The chemical companies came to the bargaining table when 1)the environmental groups blocked a bill in Congress that the companies wanted, extending patent rights, and 2)the environmental groups themselves decided that they would rather deal than flail. The amendments would not change the basic standards by which the risks and benefits of pesticides are judged. But they would set a timetable for review of the more than 600 active ingredients in pesticides already on the market; in the 14 years since Congress set this task for it, EPA has been able to make its way through only about 40 of these.

The amendments would also exact fees from manufacturers to help pay the cost of these reviews; would require EPA to regulate some of the more important "inert" ingredients in pesticides as well; and would try to hasten the cancellation process by which products found dangerous are ordered off the market. ("Chemicals get more due process in this country than people do," a negotiator for the environmental groups once said.)

The two sides are still trying to work out provisions to guard against contamination of groundwater. This is increasingly an issue in pesticide regulation. EPA is empowered in general terms to deal with it. The environmentalists would make its instructions explicit.

Pesticides are now widely regarded as one of the leading sources of danger to the environment. Farmers are said to use not only more than is safe, but more than they need to. But the instinct of farm groups is to resist steps that would either reduce the availability of these products or raise their cost. The amendments are an effort to balance competing interests in this field. They are already an impressive accomplishment. If Congress can't work out a bill with this much help, what can it do?