The authors of a Comment article note that studies extending beyond 12 months are needed to assess stents with biodegradable polymers, as once the polymer has gone, the underlying stent cannot be assumed to be equivalent to a bare-metal stent because drug effects could linger. They call for large, adequately powered, long-term studies to capture the natural history of the processes initiated by stent deployment and to investigate whether there are important differences between drug-eluting stents. They suggest that assessment of the primary endpoint at 2 or 3 years might be most useful clinically, with prespecified overall follow-up of 5 years or longer to allow time for possible benefits, such as reduced shear stress or vessel-wall inflammation, to manifest themselves clinically.