Although knowledge transfer has been recognized as one of the critical success factors in outsourcing, there is currently no work systematically reporting on how knowledge transfer is and can be managed in the firms involved in outsourcing relationships. This paper presents results of 12 case-studies analyzing knowledge transfer processes in IT-outsourcing, investigated through 48 structured interviews. The findings identify the main knowledge transfer phases and current practices between outsourcing partners. They are consolidated into a preliminary, empirically-grounded reference model for knowledge transfer in outsourcing. Special attention is given to the analysis of outsourcing-specific knowledge transfer activities and most frequently used knowledge transfer techniques. By analyzing how current practices can be effectively employed or extended to reduce outsourcing-specific knowledge-asymmetries, we provide one of the first contributions to understanding how firms can design, manage and support knowledge transfer as a strategic goal of their outsourcing relationships.