In 2011 the Belgian Obstetric Surveillance System (B.OSS) was set up to monitor severe maternal morbidity in Belgium.The aim of B.OSS is to get an accurate picture of the obstetric complications under investigation and secondly, to improve the quality and safety of obstetric care in Belgium by practical recommendations based on the results.Data are obtained through prospective active collection of cases by a monthly call according to the principle of nothing-to-report, along with data collection forms that confirm the diagnosis and gather detailed information. Data-collection occurs web-based since August 2013 through www.b-oss.be.B.OSS achieves excellent participation rates and response rates. The results of the first registration round are gradually brought out by means of scientific publications and presentations, biennial reports, newsletters and the website. The international comparison of results within the International Network of Obstetric Survey Systems (INOSS) gives important added value. No alternative mandatory data sources are appropriate to check for underreporting.B.OSS is successful in monitoring severe maternal morbidity thanks to the willingness of the Belgian OB-GYNs. The results of the first studies suggest the need to develop nationally adopted guidelines. Furthermore, the results invite to critically evaluate the current organisation of obstetric health care in Belgium. B.OSS aims to monitor the impact on patient safety in future surveys, when guidelines and recommendations are put into practice.