The objectives of this paper are both to identify the environmental motivations associated with the decision to initiate the process for ISO14001 certification and to check whether such motivations undergo any changes once the company obtains its certification and experiences the actual effects of this process. Based on the work of Bansal and Roth, we distinguish between ethical, competitive and relational motivations, and compare the importance of these motivations in four company stages with respect to the ISO14001 certification: not considered, considered, in process and awarded. This comparison was performed through a logit analysis applied over the data supplied by 184 Spanish manufacturers from three different industrial sectors. It was concluded that the decision to pursue the ISO14001 certification responds to ethical and competitive motivations, and that once the company gets its certification, the company portfolio of environmental motivations does not change significantly.