This study describes the use of preimplantation genetic diagnosis (PGD) to prevent the transmission of four lysosomal storage disorders: Tay-Sachs disease, Gaucher disease, Fabry disease, and Hunter syndrome. PGD was performed on 28 embryos from 9 couples, identifying 2 embryos with mutations and deriving stem cell lines from them. The technique was highly accurate, avoiding transmission of diseases while establishing mutant stem cell lines for research.