Background: Sleepwalking is a common and highly heritable sleep disorder. However, inheritance patterns of sleepwalking are poorly understood and there have been no prior reports of genes or chromosomal localization of genes responsible for this disorder. Objective: To describe the inheritance pattern of sleepwalking in a 4-generation family and to identify the chromosomal location of a gene responsible for sleepwalking in this family. Methods: Nine affected and 13 unaffected family members of a single large family were interviewed and DNA samples collected. Parametric linkage analysis was performed. Results: Sleepwalking was inherited as an autosomal dominant disorder with reduced penetrance in this family. Genome-wide multipoint parametric linkage analysis for sleepwalking revealed a maximum logarithm of the odds score of 3.44 at chromosome 20q12-q13.12 between 55.6 and 61.4 cM. Conclusion: Sleepwalking may be transmitted as an autosomal dominant trait with reduced penetrance. Here we describe the first genetic locus for sleepwalking at chromosome 20q12-q13.12.