The tobiano white spotting pattern is a trait controlled by a dominant gene. The pattern is clearly marked and characterized by white across the spine, extending downward between the ears and tail. The skin underlying the white spots is pink and under the colored areas it is black. The eyes are usually brown but one or both may be blue or partially blue. The head is dark, with white markings like those of a solid colored horse. Usually all four legs are white below the hocks and knees. The spots are generally regular and distinct as ovals or round patterns. The tail can be two colors, a characteristic seldom seen in horses that are not tobiano. A tobiano can be predominantly dark or white.

The tobiano gene has two alternative states (alleles). The dominant allele, TO, produces the tobiano pattern and the recessive allele, to, is non-tobiano.

A horse that is homozygous for tobiano, symbolized as TOTO, will always produce offspring that are tobiano regardless of the mate. For breeders interested in producing tobiano offspring, it is obvious that a horse that is homozygous for tobiano is desirable in a breeding program.