Because the spectrum of anorectal malformations is wide, genetic investigations of these anomalies should include the study of multigenic models presenting variable penetrance and expressivity. Current knowledge in clinical genetics, cytogenetics, and molecular genetics of anorectal anomalies are reviewed. The analysis of associated anomalies (that are found in more than 60% of anorectal malformations) is an important aspect of the molecular study, because the association of anomalies with mendelian transmission or with a recognized causative gene can be an essential starting point for further investigations. In the present study, the authors focus on associated sacral anomalies, urethral malformations, and intestinal dysganglionoses. In particular, associated sacral anomalies could be a partial expression of the Currarino syndrome, which represents the only association for which genetic evidence has been demonstrated by linkage analysis. The authors studied a four-generation pedigree with recurrence of the Currarino syndrome, and the haplotype reconstruction confirmed that the gene segregating in this family is located in the 7q36 region. The collection and study of families with multiple cases of anorectal malformations could show whether different phenotypes are caused by single genes.