The use class of biocides was studied in order to nominate chemicals as candidates for carcinogen bioassay to the National Cancer Institute. After the application of several qualifying criteria that related to previous, current, or planned carcinogenicity testing and to commercial significance, the preliminary candidate list of 295 chemicals was reduced to a list of 61 final candidate chemicals. Based upon consideration of both the suspicion of possible carcinogenic activity and evidence indicating potential human exposure, the following eight chemicals were nominated: benzethonium chloride, hexahydro‐1,3,5‐tris(2‐hydroxy‐ethyl)triazine, benzyldimethyl(mixed alkyl)ammonium chloride, N‐(3‐chloroallyl)hexaminium chloride, 2,4,5‐trichlorophenol, o‐benzyl‐p‐chlorophenol, l,2‐benzisothiazolin‐3‐one, and zinc pyrithione.