The multilateral partnership to emerge from the 1979 Air Convention as grown into an impressive structure with a number of offshoots and good results. Nine protocols have been successfully negotiated, each new step addressing new issues or representing tighter control on emission levels. The most ambitious of these protocols is the 1999 Gothenburg Protocol, revised in 2012, which is also widest in scope. Sulphur abatement has been most successful; emissions have dropped by over 70 per cent. This has led to a significant reduction in acidification-related damage in Europe. But the critical loads in the environment are still exceeded in vulnerable areas. As to important research challenges ahead, it is surely time for a new wave of in-depth country case studies, not least of the implementation of the Nox commitments agreed to under the Gothenburg Protocol. And further study of several types of policy interactions.