Fertilized eggs, of Discoglossus pictus were subjected to shock from hydrostatic pressure. The results may be summarized as follows: 1) the shock is lethal at values ranging from 200 to 300 atms; 2) relatively low hydrostatic pressures (100-80 atms) allow a normal development. The treatment may cause heteroploidy, with chromosome numbers varying between 17 and 25. However, the majority of embryos showed diploid chromosomal sets.