MEGA is the chemical workplace exposure database of the Institute for Occupational Safety (BIA) of the German Berufsgenossenschaften (BG) (statutory accident institutions for insurance and prevention). On the legal basis of the social insurance law the inspectorates of the BGs conduct workplace measurements of chemical and biological agents. The BGs have cooperated with BIA within the Berufsgenossenschaftliches Messsystem Gefahrstoffe--BGMG since 1972: measurements are done by the BGs, analyses and data processing are the tasks of BIA. In 1999 31,000 measurements with 68,000 analyses were taken in 4,000 enterprises. All data are stored in the MEGA-database with up to 150 pieces of information (describing type of workplace, working conditions, measured substances, sampling strategy, sampling duration, sampling and analytical method etc.), for each result. MEGA contains today about 1,000,000 measurements of more than 400 substances starting in 1972. MEGA is used by BIA and the BGs for the following purposes: prevention (e.g., identification of hazards, efficiency of exposure reducing measures, determination of technical criteria for exposure limit values), epidemiological questions, and investigations of occupational diseases. In the framework of the measuring and inspection activities and tasks of the inspectorates of the BGs the locations for measurements are not randomly selected, but are based on criteria such as supposed critical exposure situations or testing the efficiency of exposure reducing measures. Nevertheless, a statistical appraisal of the data is possible for different purposes considering the specific determinants of the results, as, for example, classification of enterprises (sectors), workplaces (activities, tasks), used materials, and products. The MEGA-database will be further developed into a multifactorial exposure database with additional data on biological exposure to bacteria and funghi, but also noise and other data.