In many developing countries, a host of financial, institutional, and political factors hamstring conventional environmental regulation. Given these constraints, a promising strategy for controlling pollution is to promote the voluntary adoption of clean technologies. Although this strategy has received considerable attention in policy circles, empirical research on the adoption of clean technologies in developing countries is limited. This paper presents historical background and original survey data on the adoption of five clean tanning technologies by a sample of 137 leather tanneries in Leon, Guanajuato, Mexico, a city where tanneries have serious environmental impacts and conventional environmental regulation has repeatedly failed to mitigate the problem. The analysis suggest that rather than top-down public-sector pressure and technical assistance, the key factor driving the adoption of clean tanning technologies in Leon is the bottom-up dissemination of information about the cost and quality benefits of the technologies.