The development of medicinal products is subject to quality standards aimed at guaranteeing that database contents accurately reflect the source documents. Paradoxically, these standards hardly address the quality of the source data itself. The objective of this work was to propose recommendations to improve data quality in three fields (pharmacovigilance, pharmacoepidemiology and clinical studies). The analysis was focused on the data and on the critical stages presenting critical quality problems, for which the current guidelines are insufficiently detailed, unsuitable and/or poorly applied. Finally, recommendations have been proposed, mainly focused on the origin of the data and its transcription.