Restless legs syndrome (RLS) and Tourette's syndrome (TS) share some common features, including the phenomenology of sensations relieved by movements, but few studies have examined the links between RLS and TS. We examined RLS and other TS comorbidities in 144 probands with TS or chronic tics and their parents. RLS was present in 10% of probands and 23% of parents with no gender differences. RLS in probands was linked significantly to maternal RLS but not paternal RLS, suggesting that a maternal RLS factor may contribute to the variable expression of TS.