The aim of our study is to determinate if an active educational intervention (interactive sessions discussing clinical cases plus the minimal intervention) reduces the professionals referral rate compared with the minimal intervention group (written adapted clinical practice guidelines and feedback about their referral rate compared with other primary care teams). It is a cluster-randomized controlled trial stratified by the percentage of reform and the referral rate. The subjects were primary care physicians of the 51 teams of Barcelona city attending 1.160.748 inhabitants.