Most systematic reviews rely substantially on the assessment of the methodological quality of the individual trials. The aim of this study was to obtain consensus among experts about a set of generic core items for quality assessment of randomized clinical trials (RCTs). The invited participants were experts in the field of quality assessment of RCTs. The initial item pool contained all items from existing criteria lists. Subsequently, we reduced the number of items by using the Delphi consensus technique. Each Delphi round comprised a questionnaire, an analysis, and a feedback report. The feedback report included staff team decisions made on the basis of the analysis and their justification. A total of 33 international experts agreed to participate, of whom 21 completed all questionnaires. The initial item pool of 206 items was reduced to 9 items in three Delphi rounds. The final criteria list (the Delphi list) was satisfactory to all participants. It is a starting point on the way to a minimum reference standard for RCTs on many different research topics. This list is not intended to replace, but rather to be used alongside, existing criteria lists.