A 240-day-gestation female bovine fetus with severe anasarca, palatoschisis, cheiloschisis, mild cranioschisis, and a flattened facies was collected at a slaughterhouse, and a fibroblast line was established from the fetal skin. Chromosome preparations were Q-banded, and chromosome counts were taken that indicated the presence of 61 chromosomes in cells of the fetus (the normal diploid number for domestic cattle is 60). Q-band karyotypes were constructed, and Q-band analysis revealed the presence of three copies of chromosome 20. Trisomy 20 (61,XX,+20) was confirmed through the use of two-color fluorescence in situ hybridization of bovine bacterial artificial chromosome clones that were specific to chromosome 20 and the X chromosome.