摘要Aim: To report a birth after intracytoplasmic sperm injection (ICSI) of ejaculated spermatozoa from a man with mosaic Klinefelter's syndrome detected by fluorescence in situ hybridization (FISH) analysis. Methods: A 35-yearold man with a normal appearance consulted our hospital because of sterility over a 5-year period. Chromosome analysis showed low-incidence mosaic Klinefelter's syndrome. Using FISH, 96% hyperploidy of the lymphocytes was found. We examined the sex chromosome of the ejaculated spermatozoa. Using FISH, we examined 200 ejaculated spermatozoa and no hyperploidy was found. Results: The 33-year-old female partner of the male patient underwent an uncomplicated controlled ovarian hyperstimulation sequence using a combined recombinant-follicle stimulating hormone (rec-FSH) + human menopausal gonadotrophin (hMG) protocol, following late luteal phase pituitary down regulation. This culminated in the retrieval of seven oocytes, six of which were fertilized with ICSI.One ICSI attempt led to clinical pregnancy with a healthy baby girl. Conclusion: We report a male patient with lowincidence mosaic Klinefelter's syndrome whose ejaculated spermatozoa were identified as being haploid by FISH before ICSI, leading to the successful pregnancy of his wife and the birth of a healthy baby girl.