Currently in Chile, there are about 42 nuclear medicine centres that mainly use 99mTc and 131I in diagnostic and therapeutic procedures. Therefore, staff performs various tasks that increase the risk of internal incorporation and the need to implement routine monitoring programmes. This article shows tools for self-monitoring of staff who exposed to 131I from measurements in thyroid and urine samples, using the gamma cameras of Nuclear Medicine Units. Then, the calibration factors of gamma cameras of participating units were determined, and a one-worker dose was calculated due to internal incorporation, using an Excel spreadsheet for self-monitoring. The worker who handles 131I in one of the studied units was monitored for 6 months. The goal of this study is to implement a routine self-monitoring programme for the estimation of committed effective dose of staff exposed to 131I using gamma cameras in Nuclear Medicine Units of clinical centres in Chile.