The recruitment as a process found by many authors to be undergoing of many factors. There is a factors which are decreasing the recruitment and last data is reporting up to 80% trials failed due to law or even absence of recruitment on level of sites. But the factors are differently changing the recruitment. The final number of recruitment is static figure very well known, there is also known speed of recruitment which is calculating in the start of the study and these parameters along with others is quantitative evaluation of recruitment. We investigated the rate of recruitment in the light of some factors using parameters reflecting the recruitment progress of recruitment. Materials and Methods: Retrospective analysis of data of four clinical trials II-III phases in oncology and hematology, conducted since 2007 to 2017 years. Study objectives: to investigate the study recruitment rate using different parameters and its changes along with acting of internal factors; to develop new parameters which could be sensitive for evaluation of factor’s action. Statistical analysis: data had been collected from feasibility questionnaires, open statistical sources. Results: It was determined rate of recruitment and its derivatives where was acting an internal factor. Discussion: Recruitment been undergone the internal factors. The way of action is multidirectional and could boost the recruitment and in opposite to decrease one and knowing it is important in success of recruitment and clinical trial itself eventually.