Objectives: To review the performance of research ethics committees in Spain in assessing multicentre clinical trial drug protocols, and to evaluate if they would comply with the requirements of the new EU Directive to be implemented by May 2004.Design and setting: Prospective study of applications of MCT submitted to RECs.Main measurements: Protocol related features and evaluation process dynamics.Results: 187 applications to be performed in 114 centres, were reviewed by 62 RECs. RECs had a median number of 14 members, of which (...) three were lay members. All applications were approved except four which were however approved by the other RECs involved. The median times from submission to approval and from submission to reception at the sponsor’s offices were 48 and 62 days, respectively. In 55% of all applications approved, 41 RECs raised 307 queries, 40% of these were protocol related issues, and 38% related to the patients’ information sheets. RECs charging an evaluation fee in advance and applications with no queries raised were statistically significantly associated with shorter evaluation times. However, there is a gap of at least 1.5 weeks between the date of the meeting and the reception of the approval letter in the sponsor’s office.Conclusions: Evaluating MCT protocols by RECs is a time consuming process. Needing 1.5 weeks for communicating the decision taken by RECs to the sponsor suggests serious administrative shortcomings within most RECs. By significantly reducing the time for communication of their decisions, the majority of RECs would comply with the Directive requirement of a maximum 60 day period for the assessment of MCT. (shrink)