Medical Association of the Humane Society of the United States defines the main characteristics of a puppy mill as "emphasis on quantity over quality, indiscriminate breeding, continuous confinement, lack of human contact and environmental enrichment, poor husbandry, and minimal to no veterinary care."

There are an estimated 10,000 licensed and unlicensed puppy mills in the United States, in total selling more than 2,000,000 puppies annually. In these puppy mills, breeding dogs