Hylalabialis embryowereexposed to 1.23, 1.47, 2.47, 2.95, 3.7,4.43,4.94, and5.91 ppmHg2'; 0.26, 0.52, 0.78 and 1.04 ppm Cl· and 0.38, 0.76, 1.14 and 1.53 ppm N03-, separated starting of the middle and belated blastula, during 12 days of continuosexposition. Employ mayor values of mortality were registered for individuals exposed to N03·, mayor number of alterations for the exposed to the Hg2' and minornumber to alterations and mortality for the exposed to Cl·. The reported alterations in the embryo were : changed pigrnentation (decrease), irregularities, bleedings, convulsions, escoliosis, atrophy gills, edema, edemi in the wings, thin tail and anormalities. For the different concentrations of Hg2', Cl· and NO;, the majority of the alterations present calculated val u es from t of Student larger than the critic value, corroborating this way that the used variables during this study were correlated.