Different interpretations of concomitant therapy in various types of clinical trials and non-systemic approach to revealing its nature have pre-determined the systematization and generalization approaches to its assessment. In clinical trials concomitant therapy assessment gets the most important meaning in cases when it is necessary to precisely justify, determine and closely assess its influence because such information may become the basis for further stages of clinical trial, as well as future directions of pharmacovigilance. There have been protocols and case report forms of clinical trials with different designs, performed in Clinical and Diagnostics Center of National University of Pharmacy, analyzed. Consequently, on completion of analysis there have been various approaches to understanding and using concomitant therapy at a place of study determined. The developed algorithm of the Investigator’s (or the Monitor’s) assessment of registration and clinically significant abnormality assessment helps to conduct a comprehensive analysis of clinically significant abnormality, to minimize data entry mistakes, to standardize the process of fixation and assessment of concomitant therapy according to the ICH GCP requirements developed. Implementing the developed algorithm in the system of place of study will obviously help to facilitate the Monitor’s work, as well as the work of investigators who are responsible for data capturing, data monitoring and data entry processing while conducting clinical trials.