We report on a phenotypically normal man with infertility, whose 47,XY,+mar karyotype was studied by spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH) using a chromosome-15-specific probe (LSI SNRPN). By these techniques, the marker chromosome was identified as a small inv dup (15). Possible causes for male infertility in this case are discussed.