In this review, we summarize the current genetic information on human developmental disorders found in Online Mendelian Inheritance in Man (OMIM). The OMIM catalogues human phenotypes and genotypes and relevant mouse models. Among the more than 11005 genetic disorders and loci, we found at least 1231 human conditions with known gene mutationsffWe searched for human developmental disorders that present with structural defects during the perinatal period, and identified 162 such entries. We classified these entries by phenotypic features (e.g., skeletal dysplasias, axis and laterality defects, or eye disorders) and by the type of gene mutated (e.g., genes coding for transcription factors, structural proteins, enzymes, or receptors). Thirty-eight entries have allelic variants with gene mutations causing different functional consequences, thereby altering their interactions with modifying genes. Thirty-two entries show genetic heterogeneity due to either functional redundancy of more than one gene or genes that interact in common developmental pathways. Although many different types of genes are mutated in developmental disorders, we found that the disease genes are transcription factors in 49 entries. Mouse models are available for many of the human conditions, with the majority of these mutants being secondary to null mutations. These data allow us to begin to elucidate the complex developmental pathways involved in the molecular pathogenesis of human malformations.