Purpose: To help family doctors to detect and prevent problems related to drug-drug interactions in order to attain a higher quality prescription and an improvement in patient safety. Methods: Uncontrolled study of an intervention based on quality evaluation and improvement methods. Setting: Two health areas in Murcia Region (Spain). Patients: Subjects appointed to 139 family doctors regularly using electronic clinical records (including doctors who were producing over 100 electronic prescriptions per week: 188,953 subjects and 334.088 prescriptions at the start, and 202,988 subjects and 335.198 prescriptions at the end of study). Intervention: (1) A software able to collect patients who had clinically important drug-drug interactions those that should be avoided (BOT I+ II) was designed. (2) A report on these interactions was drawn up and delivered periodically to every single doctor, including patient identification and information on the drugs involved, possible consequences, and recommendations about what to do. (3) Clinical and educative sessions given by a trained pharmacist were carried out in doctors' health centre coinciding with their delivery. Results: Drug-drug interactions pre-intervention: prevalence 1.29%; by patient at risk 6.57%; by doctor 20.2. Post-intervention: prevalence 1.06% (improvement 17.6%, P<. 000001), by patient at risk 5.17% (improvement 21.4%, P<. 000001), by doctor 17.7 (improvement 12.1, P<. 001). Conclusions: Developing this technology leads to progress in patient safety, therefore it should be extended to all our family doctors. Other technologies such as an electronic alert when prescribing should be considered, particularly for either higher frequency or important consequences interactions. (C) 2009 SECA. Published by Elsevier Espana, S. L. All rights reserved.