Accuracy of assigning foal paternity to the second serving stallion for foals whose dams had been bred to two stallions within an interval of 1 to 45 days was investigated using breeding dates from 108 equine paternity cases solved by blood typing. One hundred two of the foals were sired by the second stallion but six foals (5.5%) were excluded as being by the second sires. Thus, breeding dates are not reliable as a sole source of information to assign equine paternity accurately.