New philosophies of environmental management are being put to the test in many countries.* New ideas are needed to replace or at least flank the old command and control approach, which has lost its credibility. One of the most interesting new avenues is co-operative environmental management, whereby public and private parties work together to tackle a problem. It is interesting because it seems to be well suited to handling complex environmental problems. This kind of management makes use of the policy instrument known as the Environmental Agreement. That tool is geared to the development of sustainable procedures for working out solutions. The Environmental Agreement provides scope to deal with some essential characteristics of current environmental problems. Indeed, one of the most vexing aspects of environmental problems is uncertainty, both in the ecological sphere and with respect to the economic effects of intervention. In short, this instrument takes the unknown into account.