In 2008 I published a critique of Pierre Desrochers’s early work on industrial by-product exchanges; Desrochers has now written a reply, and this is my rejoinder. Studying by-product exchanges among firms in relation to the reduction of ecological impact of economic activities is not served by drawing them into a contest to verify a hypothesis about the superiority of the market over the state as a coordination mechanism, as Desrochers continues to do. The analysis of historical and current evidence on how such exchanges come about and cluster into larger systems is best advanced by exploring the interplay between several coordination mechanisms, as is currently done by industrial ecologists.