One reason for the low implantation rate after IVF/ET is the limiting ability of blastocysts to escape from the zona pellucida, and of nidation. This procedure can be assisted by the creation of an artificial opening in the zona pellucida before the transfer (assisted hatching). An artificial slot in the zona of 58 embryos (20 patients) was created mechanically by using Leitz Fluovert microscope and Narishige micromanipulators. From 20 embryo transfers 6 clinical pregnancies resulted (30.0% clin. preg. rate). In 4 cases women with three or more unsuccessful transfers were involved. This method should be used in classical IVF, specially in cases of repeated high quality embryo transfers which failed.