In this combined EEG and MRI study, the asymmetry of functional and structural measures in the human parietal operculum (PO) were investigated. Median nerve SEP recordings showed maximum scalp potentials over contra- (N80, N110) and ipsilateral (N100, N130) temporal electrode positions. In accordance, MRI-coregistered source analysis revealed two electrical sources in the contra- (N80, N110), and two in the ipsilateral (N100, N130) PO. The dipole orientations of the contra- and ipsilateral sources with earlier peak activation, N80 and N100, were more tangential than those of the later peaking N110 and N130 sources. The most prominent contralateral N110 source exhibited pronounced left lateralized dipole strengths in the 80 - 120 ms latency range, in contrast to symmetrical N80 and ipsilateral source responses. The asymmetry of the N110 source activity explained both the asymmetry of N110 and N100 scalp potentials. Morphometric analysis demonstrated no interhemispheric differences in the sizes of the anterior PO (aPO), containing the cytoarchitectonic areas OP3 and OP4, but left lateralized sizes of the posterior PO (pPO), which encompasses the anatomically defined areas OP1 and OP2. The N110 source was located in the pPO, and its asymmetry was significantly correlated with the structural pPO asymmetry but not with handedness and auditory lateralization. Thus, both structural and functional asymmetries exist in the human PO, and they are closely related to each other but not to measures of brain asymmetry in other functional systems, i.e. auditory lateralization and handedness.