The pollution problems in aquatic environment is getting serious in many closed or semi-closed bays in most of the countries. Aliaga Bay (Izmir, Turkey) is one of the contaminated area by domestic and several industrial facilities. For this reason, the toxic effects of the samples which were collected from six stations, diluted up to 10(-1) to 10(-3) ml in habitual sea water were determined as embryo development of Paracentrotus lividus and Arbacia lixula. According to sea urchin embryotoxicity results all water and sediment samples of Aliaga Bay assessed as toxic. EC50 of water was 9.348 and 123.7 ml/L for P. lividus and A. lixula and EC50 of sediment was 2.216 and 203.37 mg/L for P. lividus and A. lixula at Station 3. In conclusion, the present investigation has pointed out a clear response of embryo bioassays of sea urchins may be good method to evaluate the toxicity of contaminated environmental samples.