This Working Paper deals with the estimation of direct, inter-industry domestic and international R&D stocks for 25 Belgian industries over the period 1995-2007. Two categories of stocks are constructed to estimate potential rent spillovers and knowledge spillovers. Domestic inter-industry and foreign R&D stocks are weighted with Supply and Use tables and bilateral trade data to estimate rent spillovers (through intermediate consumption) and with international patent citations matrices to estimate knowledge spillovers.