From May 3rd till 24th 2003, the intensive (cloud) measurement campaign "BBC2" was held at Cabauw, the Netherlands. The BBC2 campaign was jointly organized by the University of Bonn and KNMI. The University of Bonn was coordinator of the German 4DCLOUDS-project, KNMI is coordinator of the Cabauw atmospheric research observatory and member of the Dutch CESAR consortium. Beside these two research groups a number of other institutes has joint individually, in total some 100 scientists from 20 institutes participated. As most objectives and many participants are the same as those of the Baltex Bridge Campaign (BBC) in August-September 2001 organized in the framework of CLIWA-NET and 4DCLOUDS, the campaign has been named BBC2. Although the focus of the campaign was on clouds and radiation, other subjects of research were of interest like turbulence in the atmospheric boundary layer and small scale structure of rainfall. Instrumentation deployed covers a wide range of important parameters. A number of advanced active and passive remote sensing systems was operated in Cabauw. In-situ particle probes were operated on aircrafts and from a tethered balloon. Radiation sensors for long and short wave range were mounted on aircrafts and operated on the ground. Turbulence measurements were performed on the different platforms, including the 213 m high meteorological tower. Radiosondes were launched regularly during the campaign.