Since 1983, the Sentinel Network of Laboratories, coordinated by the Scientific Institute of Public Health (WIV-ISP), collects data on 40 infectious diseases. In 2009, 102 laboratories (representing 59% of all Belgian laboratories of microbiology) participated on a voluntary basis in the surveillance system. Private or hospital laboratories were evenly distributed throughout 33 of the 43 administrative districts. Influenza A virus and Respiratory Syncytial Virus (RSV) were among the respiratory infections included in the surveillance. In this paper, we present data about these 2 viruses circulating in Belgium between week 35, 2009 and week 10, 2010.