We have tested and subsequently successfully applied a single-needle approach to obtain blastomere biopsies from human preimplantation embryos for preimplantation genetic diagnosis (PGD). The method was first evaluated in a mouse system and shown to be compatible with a high degree of in vitro and in vivo development of biopsied mouse embryos. Furthermore, we showed that biopsied mouse embryos after transfer to recipient mice underwent implantation, normal development and delivery. Litters were followed through puberty and adulthood and shown to be normal with regard to sexual function and also a panel of biochemical and morphological parameters including organ histology. Successful human preimplantation diagnosis, followed by pregnancies and birth of healthy babies, was established with two out of three couples carrying a risk to transmit chromosomal abnormalities leading to severe disease. This is the first report of the successful use of a single-needle approach in human PGD. Considering its simplicity, we conclude that the single-needle approach is an attractive alternative for biopsies in PGD.