Although policymakers and the public pay less attention to commercial real estate than to residential property, it is very important for the economy. The commercial property market is opaque, however, due to the absence of data sources. As part of a "campaign for transparency in the real estate sector", ImmobilienScout24, an online property portal, has put supply data from its rental advertisements at the disposal of scientific research. Using this data and the hedonic renting price index developed by the Cologne Institute for Economic Research (IW), the paper shows the trend in rent levels for commercial real estate in the largest German cities at half-yearly intervals from 2008 to 2013. The results suggest that the market for offices and other commercial buildings in Germany is not overheated.