Parkinson's disease (PD) is associated with abnormal visual contrast sensitivity (CS) and frequent complaints of visual disturbance. Cabergoline is a potent D(2) agonist that is efficacious for the treatment of PD and is marketed throughout Europe. We studied the effect of cabergoline on the CS of PD patients. Twenty-two patients with PD participated in this placebo-controlled double-blind study. Contrast thresholds for seven spatial frequencies were determined prior to and again during treatment. The mean CS scores for the cabergoline group worsened significantly at 6, 9, and 12c/d. These changes with cabergoline may relate to reduced perception of visual detail.