For many years, it has been good clinical practice to offer chromosome testing to women with recurrent miscarriage. This chapter addresses parental chromosome testing and describes couples carrying a structural chromosome abnormality ascertained through recurrent miscarriage work-up. Conventional parental chromosome testing is offered to couples after they have experienced recurrent miscarriage. If one of the partners carries a structural chromosome abnormality, products of conception can have a normal karyotype, the same karyotype as the carrier parent, or an unbalanced karyotype. The latter can lead to miscarriage, stillbirth or the birth of a child with major congenital impairments. Molecular cytogenetic techniques such as fluorescence in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) are improving all the time and could play a role in the future in establishing submicroscopic chromosome abnormalities, resulting in another way of assessing abnormalities which play a role in couples with recurring miscarriage (RM).