INTRODUCTION: Couples at high risk of passing on a serious genetic condition to their offspring have the opportunity to use Preimplantation Genetic Diagnosis (PGD) to diagnose a specific genetic disease on embryos obtained through in-vitro fertilisation (IVF) before a clinical pregnancy has been established. This article reports the experience of our Centre, from 1999 to 2004, in Preimplantation Genetic Diagnosis (PGD) for single gene disorders (SGD), describing strategies and overall outcome data of 222 PGD cycles performed on embryos of 158 couples for 22 different genetic conditions. METHODS: The single gene defect investigated were autosomal dominant (n=14), autosomal recessive (n=133), or X-linked disorders (n=19). Fifty-five cycles were performed for SGD combined with HLA matching. Mutation analysis of gene regions affected by mutations was carried out using both minisequencing method or multiplex fluorescent PCR. RESULTS: A total of 1683 embryos were analysed. PCR amplification was performed on 2955 blastomeres, obtaining a successful amplification in 2723 (92.1%) cells. Diagnosis was achieved for 1580 (93.9%) embryos, 380 of which where transferred to the patients in 186 cycles. Overall 54 pregnancies were established (29.0% per transfer), 10 of which resulted biochemical, 6 spontaneously miscarried, two resulted ectopic and were terminated. All ongoing pregnancies were confirmed to be unaffected and went to term without complications, resulting in the birth of 33 healthy babies. CONCLUSIONS: The present results complement other similar experiences in the field and confirm the feasibility of PGD when applied in the context of a preventive genetic service.