Depression in Parkinson's disease (PD) is associated with faster progression of physical symptoms, greater decline in cognitive skills, and greater decline in the ability to care for oneself. The depression in these patients is also frequently comorbid with anxiety. There are no trials that provide data on the impact of depression treatment on anxiety, disability, and cognition in these patients. In this prospective, 8-week, open label trial, 10 patients with PD and major depression, without dementia, were given flexible doses of citalopram. Depression improved significantly and was associated with significant improvements in anxiety symptoms and functional impairment. The drug was well tolerated. This is the first study that provides data suggesting that treating depression in patients with PD may lead to improvements in anxiety and functional capacity. As with all nonrandomized, open-label trials at tertiary research centers, many nonspecific factors may have influenced the results.