A review of main genetic factors involved in pathogenesis of recurrent abortion is presented. The prevalence of chromosomal abnormalities in spontaneous abortions and the role of parental abnormalities of karyotype is pointed out, also in relation to many recent studies. The result of 354 karyotypes performed on couples with spontaneous abortion are presented; the prevalence of chromosomal abnormalities resulted 4.2%, with 73% of translocations, either reciprocal (40%) or robertsonian (33%), and 27% of inversions. The low number of minor abnormalities (0.8%) seems to confirm their poor clinical significance.