The Dandy-Walker malformation (DWM) includes hydrocephalus, incomplete cerebellar vermis and a posterior fossa cyst. Genetic influences and recurrence risks for DWM have not been well characterized. We report a retrospective study of 21 autopsy-proven cases of DWM and review the literature regarding an additional 92 subjects. DWM represents marked genetic and etiologic heterogeneity. Recurrence risk for siblings may be high when DWM is associated with a single gene disorder such as the autosomal recessive Warburg and Meckel-Gruber syndromes. DWM may also result from chromosomal anomalies or environmental factors. When the evidence suggests that DWM has not occurred as part of a Mendelian or chromosomal disorder then the recurrence risk is relatively low (on the order of 1 to 5%). There appears to be an increased frequency of the association of DWM with congenital heart disease, cleft lip/palate and neural tube defects. Based on our study we provide guidelines for the genetic counseling of families having a child with DWM.