In the current "Knowledge-based Economy" (OCDE, 1996) transfer processes have acquired a more relevant role in society. The literature identifies many aspects of this process, with the focus for our study being organizational factors influencing knowledge transfer (KT) activities. The most frequent organizational barriers to KT in the literature are reward and incentive systems, and lack of management and administrative support (Jacobson et al., 2004). From the perspective of the area of application, KT has been mostly studied in experimental science disciplines whereas Humanities and Social Science (HSS) research has been scarce (Castro-Martínez et al., 2008). The aim of this paper is to determine the influence of organizational factors on the means and intensity of knowledge transfer among HSS research groups in the Spanish context using an approach that analyses agents at different levels (Rey et al., 2008). The sample of this study is made up of 111 research groups belonging to the HSS area of the Spanish Council for Scientific Research (CSIC), the most important public research organization in Spain. The data were gathered in two phases during May 2006 and March 2007: 1). Semi-structured face-to-face interviews with a representative of each of the research groups identified and 2) Questionnaire based on the Bozeman's categories of KT determinants (Bozeman, 2000). Results show that a focus on knowledge transfer is not related to how groups and institutes are organized. Nevertheless, this activity is correlated with economic incentives and a management adapted to the specific characteristics of the HSS area. We also show the influence of CSIC s policy and management on the informal nature of the relationships among research groups and external agents. Future research expects to contribute to a deeper knowledge about the determinants of KT activity by research groups and the mechanisms used to establish collaborations with external agents.