The U.S. lead phasedown was effective in meeting its environmental objectives, and did so more quickly with the allowance of permit banking. The marketable lead permit system was highly costeffective, saving hundreds of millions of dollars relative to comparable policies not allowing trading or banking. Estimates suggest that transaction costs brought about only a modest reduction in program efficiency. The market-based nature of the program also provided incentives for more efficient adoption of new lead-removing technology, relative to a uniform standard. Distributionally, it is likely that the program was actually more responsive to the cost concerns of small refiners than a similar uniform standard would have been. The flexibility of the program likely increased the amount of violations, however, and added an unexpected monitoring and enforcement burden. On the other hand, one of the efficiency advantages of the incentive-based program is that it provided opportunities for unanticipated means of cost-effective compliance.