The field of genetics continues to evolve at a rapid pace. The completion of the Human Genome project coupled with advancing scientific techniques has led to the explosion of genetic information and testing capabilities ranging from rare genetic conditions to common and sometimes preventable conditions. The Online Mendelian Inheritance in Man® (OMIM) found at http://www.ncbi.nlm.nih.gov/omim contains information on over 12,000 genes with known sequence. Another online resource, GeneTests, found at http://www.ncbi.nlm.nih.gov/sites/GeneTests provides reference for nearly 1,500 diseases in which clinical laboratory testing is available. This chapter reviews a variety of genetic conditions categorized by primary mode of inheritance (i.e., chromosomal, single gene, and mitochondrial disorders) and is further subcategorized by disease process (i.e., metabolic, familial cancer syndromes, hematologic disorders). For each disorder, the chromosome, gene location, inheritance pattern, incidence, clinical phenotype, laboratory findings, and treatment options are reviewed. The chapter does not encompass all known genetic conditions, but provides a general overview of a wide range of genetic conditions and various inheritance patterns extending across multiple subspecialties. The suggested reading section provides key text books and peer reviewed references for those desiring more in-depth information.