In contrast to dogs fewer hereditary disorders are known in cats. Nevertheless, much progress has been made in diagnosing and managing hereditary diseases in cats. In fact, some of them occur commonly and overall they represent an important group of diseases to be reckened with from initial wellness exam to illnesses in adult cats. There are practical and specific tools to diagnose these hereditary diseases even before a cat becomes ill. The common and practical aspects of hereditary diseases and genetic predispositions will be presented and illustrated with case examples.