The purpose of these audits was to ensure the quality, integrity and validity of investigational data. Audits were performed by control of compliance to standard operational procedures (SOPs) for Good Clinical Practice (GCP). Guidelines were proposed and established by the Food and Drug Administration (FDA) in 1977-1979 and adopted by several countries of the European Community in 1987-1989 and 1990. In Argentina, 12 on site audits of clinical trials performed between 1987 and 1990, were carried out. Basic data of GCP, audited in 58 out of 153 patients included in 12 different centers, were: protection of individual rights, compliance to standard operational procedures, adverse event reports, access to original investigational data and source document archives. The analysis of all audited data showed that patient case reports form recorded findings are credible and reliable and that researchers and monitors had conducted the study with an acceptable level in accordance to SOPs of good clinical practice. Otherwise, several in need of change to obtain better clinical data were identified: ethical committees, written informed consent, protocol adherence, data record, drug accountability, document source archives and the necessity of a thorough theorical and practical training on SOPs for GCP for researchers and monitors of clinical trials.