the objective of this work is to understand the factors that influence the motivation for sustained voluntary work at the núcleo espírita nosso lar, a spiritual organization located in southern brazil. the study was conducted using qualitative methods for ethnographic research. empirical data was collected using participatory observation techniques and in-depth interviews, as well as document analysis and information given by the managers. for the analysis and categorization of the material an analytical model developed by penner was used, composed of demographic characteristics, dispositional and organizational categories and the identity of the role of a volunteer. it was found that demographic characteristics do not influence sustained voluntary work. however, certain dispositional categories - personal beliefs and values, pro-social personality and motives connected to the volunteer - do influence the studied phenomenon. as for the organizational categories, it was concluded that organizational attributes and practices also influence sustained voluntary work. no evidence was found as to whether the relationship with the organization influenced sustained voluntary work.