In this study we present a new ???in situ??? calibration methodology establishment for activimeters ??? i.e., this equipment calibration can be made at the hospital and/or the nuclear medicine service (NMS) ??? and also the importance of considering vials radioactive residue when generating the calibration coefficient in terms of activity (NA). For the calibration, two methods are presented here: in the first, 99mTc sample activity (AC) is measured in the NMS. Then it is sent to the Instruments Calibration Laboratory (LCI/IPEN) where the reference activity (AR) is obtained under controlled conditions in a reference vial. After geometry and residue corrections, NA is calculated. In the second method, AR is obtained at the LCI, then 99mTc sample is sent to the hospital/NMS, where AC is measured and NA calculated. Calibration methodologies were applied to three NMS and to four equipment belonging to the radiopharmaceutical production facility (CR) at the Nuclear and Energy Research Institute (IPEN). Both methodologies were tested with and without residual activity corrections under controlled conditions. Variations of up to 4% were obtained.Coordena????o de Aperfei??oamento de Pessoal de N??vel Superior (CAPES)Conselho Nacional de Desenvolvimento Cient??fico e Tecnol??gico (CNPq)Funda????o de Amparo ?? Pesquisa do Estado de S??o Paulo (FAPESP)CAPES: 2215/2013CNPq: 312131/2016-0FAPESP: 15/19584-8