Reptiles are more and more common pets and, consequently, patients in veterinary medicine, so it is necessary to know their anatomical and physiological characteristics, in order to be able to recognize healthy from sick ones. Turtles, reptiles of the order Testudines, possess a unique anatomical characteristic, a shell, which protects them from predators and environmental threats. The shell is made of modified bone elements, and differs in size, color and shape. In addition to various microorganisms, inappropriate environmental conditions, nutrition or trauma can affect the appearance and efficiency of the shell. Shell diseases are often encountered in all species of turtles, especially those that live in water, and are caused by viruses, bacteria and fungi or are of non-infectious etiology. Some of these infections can penetrate deep into the layers of the shell, causing deformities of the carapace and plastron. Iridovirus (ranavirus) infections affect all types of reptiles and amphibians, causing extremely contagious diseases of the respiratory system and skin; picornaviruses cause weakness of the shell, while herpesviruses cause ulcerative lesions of the skin and shell. Numerous species of bacteria, such as Citrobacter sp., Serratia sp., Beneckea sp., in addition to predisposing factors, cause ulcerative diseases of the shell that can lead to septicemia and death. Diseases of fungal etiology are common in freshwater turtles (especially Chinese softshells), especially due to impaired immune status of the animal. Metabolic bone diseases are extremely important for reptiles kept in captivity and are common due to improper housing and feeding conditions. As the shell of turtles primarily serves to protect against unfavorable environmental conditions, it is necessary that it be healthy and without injuries that would allow the penetration of infections of various etiologies. On the other hand, inappropriate conditions of keeping and feeding also affect the quality and appearance of the shell, so it is necessary to educate owners and doctors of veterinary medicine about appropriate ways of keeping, feeding and caring for turtles in captivity.