‘Pet Therapy’ was born in 1953 in America, by child psychiatrist Boris Levinson. He experimented his own theories, testing the usefulness of animal comforts during child patients caring. While he was working with an autistic child, he realized that his dog helped the child to project his internal sensations, in fact the dog improved emotional exchanges, game abilities and created more pleasant sessions. In 1961 he coined the phrase ‘Pet Therapy’, today more properly substituted by Animal-assisted therapy (AAT). The AAT is used during daily practices by Medical professionals with specific experiences on this field. The AAT is supported by Animal-Assisted Activities (AAA) that “provide opportunities for motivational, educational, and/or recreational benefits to enhance quality of life”. AAA are delivered in a variety of environments by a specially trained professional, paraprofessional, and/or volunteer in association with animals that meet specific criteria. Some years ago a law established officially ‘Pet Therapy’ usefulness among medical therapies of National Health System. Today that law represents an important recognition for the well-known therapeutic value of animals in established medical treatments and it permits the official use in hospitals, institutes and retirement homes.