In this issue, Kane et al¹ (see p 485) report a systematic study of the value of magnetic resonance perfusion-weighted imaging (PWI)–diffusion-weighted imaging (DWI) mismatch to predict the clinical response to thrombolytic treatment in patients with acute stroke. The author’s main conclusion on this crucial question is straightforward: it is not prime time to use the identification of mismatch as a guide to therapeutic decisions. Buttressing this recommendation on methodology used by the Cochrane Study Group, the authors correctly ward off the premature acceptance of inadequately proven techniques. This systematic analysis is timely and concise but …