Stress can be reduced during transport and handling by training people to use behavioral principles when handling animals, selecting livestock with a calm temperament and using well designed handling facilities and vehicles. In the U.S., there are increasing problems with very excitable cattle and pigs which are very difficult to handle and drive. Gentle, quiet handling of excitable genetic lines of pigs in single file races in a high speed slaughter plant is extremely difficult. Excitable pigs are more easily distracted by small distractions such as a sparkling reflection on the floor and are more likely to balk and pile up. Some excitable genetic lines of pigs have greatly elevated death losses during transport. Excitable animals are more fearful of novel new situations than calmer genetic lines. Similar excitability problems are being observed in cattle. Excitable genetic lines of cattle are more likely to severely injure themselves or handlers during handling because they are more likely to panic when confronted with novelty. The author has observed cattle from excitable genetic lines that went into a total panic when they were in novel surroundings. Excitability problems are more likely to cause problems in the U.S. due to very extensive raising of cattle. Excitable cattle that are reared intensively become accustomed to people and vehicles and they are more tolerant of novel situations than excitable cattle reared on open rangeland where they seldom see people. Excitable genetic lines of cattle which are completely halter broken become trained to accept novelty and will usually remain calm, but when these same animals are raised extensively where they seldom see people, they often panic and injure themselves when they are brought to an auction market or slaughter plant. Breeders need to select animals that have a calm temperament. Recent research in our laboratory has shown that the position of the spiral hair whorls on the foreheads of beef cattle is related to temperament. Beef cattle with high hair whorls located above the eyes become more agitated during restraint in a squeeze chute compared to cattle with hair whorls located between or below the eyes. Indiscriminant selection for rapid growth and leanness has contributed to this problem. Excitable genetic lines of cattle and pigs are causing serious welfare problems during handling in the U.S.