Recent studies have reported an increased risk to develop Parkinson's disease (PD) in patients with idiopathic RBD (iRBD). Midbrain hyperechogenicity is a common transcranial sonography (TCS) finding in PD and has been suggested as a PD risk-marker in nonparkinsonian subjects. The objective of this study is to assess midbrain echogenicity by TCS in patients with iRBD and compare the findings with the healthy controls. TCS was performed in 55 iRBD patients and in 165 age and sex-matched controls. The area of echogenicity in the SN region in the iRBD group was significantly increased compared with the control group (P < 0.001). About 19 (37.3%) of patients with iRBD were found to have SN hyperechogenicity when compared with 16 (10.7%) of the controls (P < 0.001). This is the first case-control study assessing midbrain echogenicity in a large iRBD cohort compared to age- and sex-matched healthy individuals. The finding of an increased prevalence of hyperechogenicity in a subgroup of individuals with a priori increased risk for PD supports the potential role of hyperechogenicity as a risk marker for PD. The prospective follow-up of this iRBD cohort is needed to establish if those with midbrain hyperechogenicity will go on to develop clinically defined PD or not.