According to the American Pet Products Manufacturers Association, Americans spent more than $20 billion on pet food and supplies in 2003. Another $1.5 billion was spent that year purchasing pets. Animal rights groups and many welfare organizations are critical of pet stores that sell animals, particularly those that sell puppies (due to concerns about puppy mills) and exotic animals. The two largest companies in the pet supply industry are PETs-MART and PETCO Animal Supplies.

PETsMART was founded in 1987. According to the financial company Hoover's, the pet store had nearly $3 billion in sales in 2004 at more than 640 stores in North America. PETsMART has never sold dogs and cats. Instead, it allows local animal shelters and rescue groups to set up adoption centers in its stores to adopt these animals directly to the public. As of February 2005, PETsMART reported that this program had resulted in the adoption of 2.1 million dogs and cats. The company does sell small animals (such as gerbils and hamsters), reptiles, fish, and birds. This has drawn criticism from animal rights groups such as PETA. On its Web site, PETA says that these animals are purchased by PETsMART from commercial breeders and often suffer during their captivity from stress, injuries, and illnesses.

PETA is much more critical of PETCO Animal Supplies, a company founded in 1965. Hoover's reports that PETCO had $1.6 billion in sales in 2004 at more than 650 stores. PETCO does not sell dogs and cats, but, like PETsMART, it sells rodents, birds, and fish. After receiving complaints from customers about animal care at various PETCO stores, PETA launched a public relations campaign against the company in 1994, nicknaming it "PETNO" and setting up a Web site that listed the alleged complaints. The most serious allegations involved the refusal of store managers to pay for veterinary treatment for sick birds or to humanely euthanize those that were critically ill. PETA said that there were numerous incidents in PETCO stores in which very sick birds were placed in store freezers to die.

In May 2004 PETCO paid more than $900,000 to settle two California lawsuits accusing the company of mistreating animals and overcharging customers. The suits were filed by district attorneys or city attorneys representing San Francisco, San Diego, Los Angeles, and Marin and San Mateo counties. In August 2004 PETCO announced a new partnership agreement with the San Diego Humane Society to provide the animal organization with one million dollars in support.

In 2005 PETA's Web site claimed that PETCO had a very poor record of providing proper veterinary care, housing, food, and other services for the animals that it sells. PETCO denied these allegations and insisted that it cares for its animals properly. The company also pointed out that it donated more than $21 million to animal welfare organizations between 1999 and 2005 and has allowed animal shelters and rescue groups to hold adoptions in its stores. As of 2005, PETCO was one of the corporate sponsors of the Web site www.petfinder.org, which lists thousands of pets up for adoption by shelters and rescue groups across the United States and in Canada.