Overall frequency of major chromosomal aberration in patients with defective reproductive success is 13.1%, which suggests that fertility or sterility problems are one of the most certain symptoms for the chromosomal aberration. The reported frequency of chromosomal aberration in general population was less than 1%. A cause for the repeated spontaneous abortion and/or malformed child and sterility problems in 18.0% of couples is also chromosome abnormality. Chromosomal disorder in couples seeking IVF and ICSI is considerable (22.2%). From the genetic point of view, infertility patients seeking assisted reproduction have to be classified as a high-risk group. The incidence of chromosome abnormalities in the group of infertile men is also increased -17.7%, and within the subfertile female group it is 26.4%. The most commonly involved chromosomal aberrations in subfertile and sterile males and females are sex chromosomes. We conclude that major chromosomal disorders are the underlying basis of infertility and sterility in a higher proportion of cases than had previously been expected. It seems that the prevalence of aberrations is slightly increasing with time. A detailed cytogenetic analysis of both males and females with the decreased reproductive fitness is essential for predicting the success of reproduction