Objectives: To evaluate Primary Care Physician's (PCP) awareness degree concerning their patient's participation in Clinical Trials (CT) analyze the communication methods used and obtain physicians personal views. Methods: Authors performed a cross-sectional observational study that included CTs approved by the Institutional Review Board at a Regional University Hospital (n=78). Among these 37 CTs were selected. PCPs involved in these trials received a questionnaire regarding aspects of the CTs in which their patients participated. The communication systems established in the study protocols were analyzed. Results: Out of 89 PCPs contacted, 82.1% were aware of their patient's participation in CTs. The information reached them through verbal communication from the participant (56.3%). PCPs also accessed it through electronic medical records (EMR) (34.0%). A majority (97.4%) considered being informed about the participation of their patients in CTs should be compulsory. Conclusion: Communication of patients' participation in CTs fundamentally takes place through a verbal interaction between patients and their doctor. PCPs consider that the preferred method of communication would be an alarm system in the patient's EMR. Keywords: Clinical research, Sponsor, Electronic medical record, Safety