The etiology of obsessive-compulsive disorder (OCD) has not been clarified. This study aimed to investigate the cognitive, neurological, electrophysiological functions which are reflected in executive functions, memory, visuospatial integration; neurological examination and auditory event related potentials (AERP) (N100, N200, P200 and P300) in patients with OCD, their siblings, and control subjects and to determine potential endophenotypic markers. Thirty-three patients with OCD, 18 siblings and 21 controls; matched for age, gender and years of education were included. Yale Brown Obsessive Compulsive Symptoms Checklist Scale, Hamilton Depression-Rating Scale, an exhaustive neuropscyhological test battery and Neurological Evaluation Scale were administered. Their AERP recordings were obtained. Executive functions and visuospatial integration were highly impaired in patients and slightly in their siblings compared to controls. P200 amplitude was sorted as siblings > patients > controls. P300 amplitude was sorted as patients < siblings < controls. Neurological Evaluation Scale scores were lower in patients compared to siblings and controls. The logistic regression analysis showed that, higher P300 amplitude, better performance on block design test and faster completion of Stroop test would predict being in the control group, whereas higher P200 amplitude would predict being in the case (patient and sibling) groups. We suggest that these seem to be the potential endophenotypes of OCD. (C) 2016 Elsevier Ireland Ltd. All rights reserved.