Chromosomal abnormalities are one of the factors known to interfere with normal embryo development; thus preimplantation genetic diagnosis (PGD) for chromosome anomalies may be a new tool for improving the pregnancy rate in selected groups of patients. Embryos from three groups of patients (control, aged and recurrent miscarriage patients) were screened by PGD using specific DNA probes for chromosomes 13, 16, 18, 21, 22, X and Y. The control and aged groups were included in the PGD study because the women carried sex-linked genetic disease. The frequencies of chromosome anomalies observed in older women (46.3%) and in recurrent miscarriage patients (53%) were significantly higher (P < 0.05) than the frequency in the control group (19.3%). After PGD screening and transfer of normal embryos, pregnancies were obtained in women who had undergone repeated abortions (approximate 25% pregnancy rate per transfer) but not in older women. On the basis of these data, it seems that PGD screening of embryos can help some women undergoing repeated abortions, as these techniques allow successful pregnancies to be obtained or, if no pregnancy can be obtained, the results may help the couple to decide whether to enter an embryo or gamete donation programme.