Psychopathology of obsessive compulsive disorder (OCD) that has been characterized by a conflict between the ego and superego on one hand, and aggressive and sexual impulses emerging from the id on the other, and employment of characteristic defenses to combat intense conflicts being connected with ones' biological disposition from the psychoanalytic school of thought now gets empirical foundation from neuroimaging research. The findings disregard the psychological construct, exclusively establishing the neurobiology of the disorder. With the objective to study the impact of sexual and aggressive impulses on the executive functions and processing speed in the patient group, 20 OCD patients (11 males, 9 females) and 20 normal control subjects, matched for all relevant variables including age, sex, educational level and handedness were studied. Sexual impulse and guilt was assessed on the Sex Guilt Rating Scale (SGRS), aggressive impulses were tested using State-Trait Anger Expression Inventory (STAXI), the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) was used to assess symptom severity, executive functions were assessed through Wisconsin Card Sorting Test (WCST), and processing speed was assessed by employing the Processing Speed Index (PSI) - from WAIS III. It was found that the OCD group differed significantly from the controls, attaining significantly lower percentiles on Processing Speed Index and for all variables of WCST under consideration, namely, perseverative response, perseverative error, non-perseverative error, conceptual level response and number of categories completed. They reported higher scores on subscales of STAXI, specifically related to trait anger and lower scores on anger expression. On the items of SGRS, the OCD group significantly differed with the controls, expressing greater sexual inhibition. In conclusion, we propose an explanation of psychopathology of OCD, which addresses instinctual impulses, executive functions and neural substrates. Our findings contribute to understanding instinctual impulses from the neuropsychological perspective. The findings have implications for better eclectic understanding of the pathogenesis of OCD. © 2010 Elsevier B.V.