Preimplantation genetic diagnosis now represents an alternative reproductive option for parents at high risk of having offspring affected with certain genetic diseases. Progress in the past year has included increasing reliability in embryo sexing by both polymerase chain reaction and fluorescent in situ hybridization techniques; delivery of babies free of specific diseases such as cystic fibrosis, Lesch-Nyhan syndrome, and Tay-Sachs disease; and successful development of molecular techniques for detecting common diseases such as fragile-X syndrome. In addition, sperm separation in combination with preimplantation genetic diagnosis appears to be an exciting advance in yielding more in vitro fertilization female embryos for transfer and subsequent pregnancy in families at risk for X-linked diseases. Accumulated world experience can now be reviewed to provide couples considering preimplantation genetic diagnosis with observed pregnancy rates and accuracy of diagnosis.