Mendelian diseases are genetic disorders caused by mutations at individual gene loci that are passed down according to Mendelian patterns of inheritance. There are four main types of inheritance: autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive. Examples of each type of inheritance pattern and the probability of offspring being affected are provided. Prevention and control of Mendelian diseases includes general health promotion, early diagnosis and treatment, rehabilitation, and genetic counseling.