OMIM is a compendium of human genes and genetic phenotypes. The full-text, referenced overviews in OMIM contain information on all known Mendelian disorders and over 12,000 genes. OMIM is authored and edited at the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, under the direction of Dr. Ada Hamosh. This database was initiated in the early 1960s by Dr. Victor A. McKusick as a catalog of Mendelian traits and disorders, entitled Mendelian Inheritance in Man (MIM).

The OMIM data are separated into three separate tracks:

OMIM Alellic Variant Phenotypes (OMIM Alleles) - Variants in the OMIM database that have associated dbSNP identifiers.

OMIM Gene Phenotypes (OMIM Genes) - The genomic positions of gene entries in the OMIM database. The coloring indicates the associated OMIM phenotype map key.

OMIM Cytogenetic Loci Phenotypes: Gene Unknown (OMIM Cyto Loci) - Regions known to be associated with a phenotype, but for which no specific gene is known to be causative. This track also includes known multi-gene syndromes.

Clicking into the individual tracks provides additional information including display conventions.