This study was designed to investigate the possible genotoxic and teratogenic actions of diphenyl (DP), diphenyl ether (DPE), and their eutectic mixture, in a comparative approach including different test systems. Two microbial systems and a metazoan model were used: (1) diploid D7 strain of Saccharomyces cerevisiae; (2) Salmonella typhimurium strains TA100, TA98, TA1535, TA1537, TA1538, TA1532, TA2636; and (3) sea urchins (Paracentrotus lividus and Sphearechinus granularis). Both compounds resulted in severe toxicity in all of test organisms at levels greater than or equal to 10(-5) M (approximately 2 ppm). DP caused genetic effects in yeast with and without activating system, while the two chemicals appeared to be ineffective in Salmonella up to toxic levels. The action of DP and DPE on sea urchins resulted in developmental defects and mitotic abnormalities, following exposure of embryos or by pretreatment of sperm or eggs. In this system DPE appeared to be more effective than DP by about one order of magnitude (minimal active concentrations: 10(-5) M vs 10(-4) M). The eutectic mixture, industrially used as a heat transfer medium, was tested in its virgin and used form, for genotoxicity and embryotoxicity. The latter appeared to be more effective than the virgin eutectic. This increase in the embryo- and genotoxicity of the used eutectic may be related to the appearance of newly formed compounds in the heat transfer process. These compounds have been separated by high-pressure liquid chromatography and detected by fluorimetry.