Many organisms are in use to test pollutants and their extensive variability clearly emerges from reviews since researchers in the world are involved in continuous effort to set up new assays and to improve those already in use. In the present paper we focus the attention on the mixed function oxidase system and the DNA adduct formation which are two biomarkers widely used and extensively studied in mammals and fish by different Authors. We compare their results with the ones we obtained in amphibians, which result to be a good model. Moreover we present some significative results obtained by the use of cultured cell lines to test the herbicide MCPA. The results obtained demonstrate that the amphibian Xenopus is a suitable indicator for induction of cytochrome P-450 by B[a]P as well as for production of DNA adducts. Cultured cells evidenced that cytoskeletal array and thiol proteins are molecular targets of the herbicide used, demonstrating that risk assessment can be properly analysed in in vitro systems.