The Preimplantation Genetic Diagnosis International Society (PGDIS) was organized in October 2002, with the purpose of encouraging and co-ordinating research, education and training in this multidisciplinary field, requiring a close collaboration of obstetricians, fertility specialists, embryologists and human geneticists. One of the major tasks of PGDIS is to advance the safety and accuracy of PGD and to encourage its adoption into clinical practice for improvement of genetic practices and reproductive medicine. In this context, PGDIS published voluntary guidelines applicable for any centre offering PGD in 2004, and these guidelines are now being updated and extended based on the present extensive PGD experience. The application of these guidelines is intended to further benefit patients and provide guidance to the laboratory staff. As in previous guidelines, PGDIS presents this document being aware that differences in national regulations exist that can affect local PGD practice. The document contains recent consensus points of general application that promote quality biopsy procedures and laboratory practice, enabling PGD centres to offer an improved clinical outcome to their patients. A variety of aspects related to a safe working system have been taken into consideration, based on the assumption that a quality programme depends on the cooperation of the whole PGD team.