Hydrostatic pressure has been used to induce triploidy in Xenopus laevis. Five minutes after artificial insemination the eggs were pressurized for 5 min. The best results were obtained at pressures of 400 and 450 at when up to 97% triploids were found amongst the normal embryos and tadpoles. This method is compared with temperature shock experiments of X. laevis eggs and to results obtained by subjecting Rana pipiens eggs to pressure.