This study was developed at IPEN-Institute of Energy and Nuclear Research more specifically in CR-Center of Radiopharmacy that conducts research and processing of radiopharmaceuticals such as 99 Mo, 131 I, 123 I, 67 Ga, 201 Tl, 18 F, 177 Lu and 153 Sm for use in nuclear medicine. The radioisotopes are produced on industrial scale and the facility was designed to meet the standards of radiation safety requirements and quality control. To ensure the production, there are qualified professionals who perform the maintenance tasks of the equipments and instruments, in the radiopharmaceuticals processing cells, to conduct the work with quality and safety. This study were based in a research called "Search of Variables", for the operations carried out in restricted areas of CR, taking into account the doses distribution data for these tasks, from 2005 to 2011. This research aims to identify and determine the key variables that impact on the worker's dose. The results were presented for the following variables: Individual occupationally exposed-IOE, operation variable, Area/Cell, Type of Task and Duration of Operation, which depend on the variable Dose. The main objective is to contribute to the improvements in operations in restricted areas that may result in lower individual doses without causing significant changes in the working routine. The results have shown the variable that most affect the dose of the workers, which are: the variable Operation, the variable Area/Cell and the variable Type of Task.