A survey of the literature shows that organic and inorganic compounds of 53 metals have been assayed for genotoxic effects in vitro and in vivo. It is falund that there are great variations in the response obtained with different test systems and that a wide range of compounds of the different metals is positive in at least one of the short-term tests. Some of the variation observed could be due to differences in uptake mechanisms. This effect plus the wide variation in the quantity and quality of the data ]prevents any direct comparison of in vitro activity with in vivo potency of the various imetallic species. Downloaded from Group 5. Mutation Tests Using E. coli E. coli is used for detection of mutagenic activity in the same way as S. fyphimurium. Different strains of E. coli detect forward as well as reversed mutations. Three essentially different test pro-Address reprint requests to: