Background: Cancer is the third cause of death in Iran. Oncologists play a key role in declining the mortality rate of cancer. Objectives: This study aims to accurately estimate oncologists' active supply by using 3 sources of capture-recapture (CRC) in Iran. Methods: This was a cross-sectional study in 2015 targeting all oncologists in Iran registered in 3 independent sources, a hospitals national survey (213), database of Iran ministry of health and medical education (180), and the database of continuing medical education (173) were used to identify number of oncologists that were active. Duplicate records between the 3 sources were identified and removed using the Microsoft Office Access software. Medical council codes, names, surnames, as well as national ID codes were used for data linkage between the 3 sources.