Michael Porter and Claas van der Linde have written a paper that is in­teresting and, to us at least, somewhat astonishing. It is a defense of environmental regulation-indeed, an invitation to more stringent reg­ ulation-that makes essentially no reference to the social benefits of such regula­ tion. This approach contrasts starkly with the methods that economists and other policy analysts have traditionally used when assessing environmental or other reg­ ulatory programs.