This year's winner is two-year-old Peanut, whose wild white and brown hair, bulging eyes and protruding teeth belie his sweet, energetic personality.
Peanut's owner, Holly Chandler of Greenville, North Carolina, says he was seriously burned as a puppy and she wants to use her pet to raise awareness about animal abuse.
She plans to use the 1,500-dollar (£880) prize to pay for other animals' vet bills.
The contest, held at the Sonoma-Marin Fairgrounds in Petaluma, California, is in its 26 year.
The dogs are scored by a three-judge panel in several categories, including special or unusual attributes, personality and natural ugliness.
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