Apathy is a salient feature of various neuropsychiatric disorders, from depression to Alzheimer's disease. We formally assess its prevalence in idiopathic Parkinson's disease (PD) together with its clinical, neuropsychological, and morphometric correlates. Thirty patients with PD and 25 normal controls were assessed using an extensive neuropsychological battery and Marin's Apathy Scale; parkinsonian patients also underwent MRI scan, followed by linear measurement of various frontotemporal structures. Approximately 45% of the PD sample showed apathy. For comparison analysis, given the unimodal distribution of the apathy scores, the PD sample was divided into three groups on the basis of the apathy tertiles. All three PD groups had worse cognitive and depression scores than controls, whereas they did not differ in terms of demographic, neurological, general cognitive, or affective features. By contrast, a significant positive association was found between apathy scores and performance on tests of executive function. As regards the morphometric data, we failed to find any specific measure of frontotemporal atrophy correlating with the presence or severity of apathy. Thus, apathy seems to be a frequent and important companion of PD, in many cases probably due to a primary motivational impairment, possibly related to a frontosubcortical dysfunction. © 2002 Movement Disorder Society.