BACKGROUND: Triploidy may arise from fertilization of a mature haploid egg by two haploid sperm or by failure of meiotic divisions yielding a diploid gamete. We encountered a couple with habitual abortion, in which the last two fetuses were documented as viable triploid. METHODS: To avoid dispermic penetration and development of abnormal preembryos, insemination was done by intracytoplasmic sperm injection (ICSI) followed by fluorescence in situ hybridization (FISH) of biopsied blastomeres. RESULTS: Tests of the husband's spermatozoa by FISH, revealed that only 2-3% of the sperm were disomic for chromosomes 16, 13, 21, X, and Y. No triple disomy was detected among chromosomes 16, 13 and 21, which makes it very unlikely that triploidy resulted from diploid spermatozoa. Following a controlled ovulation induction protocol, low quality oocytes with immature cumuli were revealed. After ICSI, five eggs became two pronuclei (2PN) zygotes and none of the other eggs developed a 3PN zygote. FISH was performed on chromosomes 16 and 21 in four preembryos developed to a 6-8 cell stage. Aneuploidy or mosaicism for each of these chromosomes was detected in one preembryo and later in two disaggregated blastocysts. FISH failed in one preembryo that became atretic after biopsy. CONCLUSIONS: Although this case was unsuccessful in achieving embryo transfer and normal pregnancy, we detected many abnormal morphological features in the oocytes and chromosomal abnormalities in the cleaving preembryos. This protocol can be proposed to patients with recurrent pregnancy loss associated with chromosomal abnormalities in the fetus.