Genodermatoses are a large group of inherited single gene disorders with skin manifestations and the recognition of these cutaneous findings is important for the detection of other associated abnormalities in these frequently multisystem disorders. The initial portion of the chapter deals with the principles and terminologies in genetics along with the salient features of the various modes of inheritance. A pictorial representation of the symbols used in family pedigree is provided. The second portion of the chapter provides the significant features of selected genodermatoses with clinical photographs which includes neurofibromatosis, tuberous sclerosis, von Hippel-Lindau disease, Sturge-Weber syndrome, xeroderma pigmentosum, and incontinentia pigmenti. Neurofibromatosis and tuberous sclerosis, the most commonly encountered neurocutaneous syndromes are discussed in great detail with emphasis on description of the clinical manifestations and diagnostic criteria.