The reuse of routine healthcare data for research purposes is chal-lenging not only because of the volume of the data but also because of the va-riety of clinical information systems. A data warehouse based approach enables researchers to use heterogeneous data sets by consolidating and aggregating da-ta from various sources. This paper presents the Enterprise Clinical Research Data Warehouse (ECRDW) of the Hannover Medical School (MHH). ECRDW has been developed since 2011 using the Microsoft SQL Server Data Ware-house and Business Intelligence technology and operates since 2013 as an in-terdisciplinary platform for research relevant questions at the MHH. ECRDW incrementally integrates heterogeneous data sources and currently contains (as of 8/2018) data of more than 2,1 million distinct patients with more than 500 million single data points (diagnoses, lab results, vital signs, medical records, as well as metadata to linked data, e.g. biospecimen or images).