Experiments were carried out: on the effect of some pesticides on the embryonic development of fertilized eggs from the sea urchin Lytechinus variegatus Lamarck, Var. Atlanticus. The eggs were fertilized in a ''nursery'' specially designed for such purpose. Three minutes after the formation of the fertilizing membrane, suitable amounts of Trifluraline, Folidol 600, Goal, Roundup, Sulfosate and K-Otrine were added to the fertilized egg and their effect observed by microscopic examination. It has been found that specific alterations on the embryonic forms of the egg development were caused by the different pesticides used. The observation begun after the addition of the pesticide to the egg suspension and was carried out for 24 hours, up to the stage of pluteus.