Although many logistical issues must be consideredin the design of proceduralRCTs, including the feasibilityof blinding and the balance of internal and externalvalidity, timing of evaluation has a particularlypowerful influence on both the feasibility and results.ProceduralRCTs can be undertaken too early or too late.On one hand, as soon as clinicians and patients areequally unsure which of 2 treatment strategies is best(ie, equipoise is established), they would like to beginclinical trials.Onthe other hand, unlikedrugs that are uniformin their composition and are thus standardized atthe point of licensure, procedures are delivered by physicianswhoneedto develop technical proficiency, a processthat occurs over time. As such, procedures requirematuration before theyare ready forevaluation,whereasmost drugs have no such learning curve. As a result,evaluating the efficacy of effective procedures too earlyin theirdevelopmentmaylead to type2errors.This problemmay have occurred when studying extracorporealmembrane oxygenation for acute respiratory distresssyndrome.3 The trial was criticized because of the highnumber of complications in both groups and the lack ofprior experience in the majority of study centers. Thus,giventhecomplexityof usingthe technology, it is not surprisingthat this trial failed to show significantly improvedoutcomes, whereas later studies showed morepromising results