The article examines the effects of environmental regulation in the adoption of technologies to reduce discharges by industries in Santander, Colombia, in relation to other decisive factors such as market and community pressure. It also contains an evaluation of the way in which entrepreneurial capacity, the policy style of the regulator and the degree of interaction of enterprises in innovation networks affect the degree and direction of the adoption of technologies. For this purpose, original data from interviews and surveys are used. The results show that investment in environmental technology is explained largely as a response by businesses to pressure from direct regulation, and that the larger the business, the greater the effect. In order to reduce additional costs associated with the payment of the effluent charge, some businesses have adopted good housekeeping practices, and recover by-pro-ducts of the treatment of their waste water. This study provides evidence of the growing role of the regulator as a source of technical advice for business. Finally, results confirm that the ability of businesses to access networks and to reap the benefits of their interaction depends on the capacities which encourage innovation.