Although previous studies of Gillespie syndrome have systematically reported a generalized delay of cognitive development (mental retardation or oligophrenia), psychometric data to substantiate this view are strikingly absent. In the present study two first degree relatives (mother and daughter) with Gillespie syndrome were neuropsychologically investigated. Aside from a marked asymmetry in the Wechsler-IQ profile, consisting of significantly better results on the verbal [Verbal IQ (VIQ)] than on the nonverbal part [Performance IQ (PIQ)] of the test, cognitive and behavioral assessments revealed a pattern of abnormalities that closely resembles the “cerebellar cognitive and affective syndrome” (CeCAS) (Schmahmann and Sherman, 1998). Aside from prefrontal dysexecutive dysfunctions such as disturbed cognitive planning and set-shifting, parietal lobe involvement was reflected by impaired visuo-spatial memory and visuo-spatial disorganization in constructional tasks. Within the linguistic domain involvement of the prefrontal and temporal language regions was indicated by impaired letter fluency, incidences of agrammatism, apraxia of speech and disrupted language dynamics. With regard to mood and behavior, a number of personality and affective characteristics were found that are typically associated with prefrontal lobe damage and dysfunction of limbic related regions in the cingulate and parahippocampal gyri. Disinhibited symptoms characterized behavior and affect of the mother while the daughter displayed a variety of inhibited symptoms. As a result, behavioral and cognitive findings in these patients do not support the prevailing view of a global mental retardation as a cardinal feature of Gillespie syndrome but primarily reflect cerebellar induced neurobehavioral dysfunctions following disruption of the cerebrocerebellar anatomical circuitry.