Inhabitants (1177) of a residential area in Frankfurt/Main have been investigated with respect to internal exposure to pyrethroids. Biological monitoring revealed a body burden of pyrethroids. The 95th per thousand for the urinary metabolites of pyrethroids, such as permethrin and cypermethrin, cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis-DCCA and trans-DCCA), was determined to be 0.5 and 1.4 microg/l, respectively. 95th per thousand for cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (DBCA), a specific metabolite of deltamethrin, and 4-fluoro-3-phenoxybenzoic acid (F-PBA), a metabolite of cyfluthrin, were 0.3 and 0.27 microg/l, respectively. The metabolic pattern found for these samples points out that pyrethroids are probably ingested orally with daily diet.