The animal humanization, of pets in particular, is a current topic today. It is the subject of broadcasts, debates involving economists, psychologists, lawyers, doctors, clergy, philosophers and anthropologists, and has became a driver for the expansion of markets, investment policy and artistic inspiration. But how is the #humanity# of these animals produced? When or how far are they human? The aim of this thesis is to bring up these negotiations and limits, arguing that what we address as humanization of animals is not only nurtured of the equivalence of cultural elements - such as human names, clothing, care, the fact that they live in the same households or for motivating discussions on some rights and morals. Likewise, it#s nurtured of those elements that we attribute to the field of nature, as some instincts that need to be modulated or an equivalent biology that allows the diagnosis of organic problems and their medicalization. Thus, the reflections presented here are result of an ethnography that ranges from the anthropological literature regarding the location or status of the animals and their relationships with humans, to a fieldwork consisted of following veterinarians in their professional endeavors, in pet shops comprising veterinary clinics.