Ataxia Telangiectasia (AT) is an autosomal recessive disorder with an incidence estimated at 1 in 40 000 to 1 in 100 000 live births. More than 100 different somatic and germ-line mutations have been identified in the AT gene, the majority of which cause premature protein truncation. The immense size of the AT gene (66 exons) complicates the detection of mutations. A Saudi family with three affected children suffering from AT consulted our IVF centre for preimplantation genetic diagnosis (PGD). Despite advanced maternal age and unknown mutation, the family was screened for AT mutations. A large deletion in the gene was found to be responsible for the phenotype of AT. The mutation detection permitted us to perform PGD on AT for the first time. Single cell PCR consisted of amplifying one of the deleted exons, exon 19. Homozygous affected embryos show an absence of the exon, while in heterozygous or normal embryos the exon is amplified successfully. After ICSI, three embryos were suitable for embryo biopsy. After biopsy only one embryo showed exon amplification and was transferred. A singleton pregnancy ensued and prenatal diagnosis confirmed the presence of exon 19. This report demonstrates that PGD is feasible despite advanced maternal age and poor response to follicle stimulation.