This chapter deals with the health and medical care issues of guinea pigs. Guinea pigs have wide bodies with short limbs. They have a short, flat nose, laterally placed eyes, and hairless external pinnae. The dentition of the guinea pig is described as aradicular hypsodont. Guinea pigs are best housed in well-ventilated, wire-sided cages with solid bottoms. If housed indoors, guinea pig enclosures do not require a cover, as these animals do not typically jump or climb. Heavy food containers are recommended to make dumping of the receptacle more difficult. All food containers should be easy to disinfect and should be cleaned regularly, because guinea pigs have a habit of soiling their food bowls. These animals, native to the Andes Mountains, are very susceptible to hyperthermia and should never be housed in temperatures greater than 80°F. High humidity can also exacerbate a guinea pig's sensitivity to elevated temperatures by increasing the heat index. Guinea pigs often do not exhibit clinical signs early in a disease process. Therefore, a thorough physical examination can be extremely useful in determining the overall health status of the animal.