We studied the effectiveness of cabergoline as an adjunct in patients with early Parkinson's disease receiving another dopamine agonist (pramipexole or ropinirole), at the maximal permitted dose. The study enrolled 47 patients: 35 had motor fluctuations and were receiving a dopamine agonist with levodopa; and 12, without motor fluctuations, were receiving a dopamine agonist without levodopa. These medications had in all cases failed to achieve adequate symptom control. In the 35 patients with motor fluctuations, when cabergoline was added to therapy, the time spent in the OFF period decreased by 65.6% (from 3.14+/-1.11 to 1.08+/-1.07 hours p<0.0001); and the Unified Parkinson's Disease Rating Scale (UPDRS) motor score decreased by 19.24% (from 41.68+/-12.6 to 33.66+/-10.22; (p<0.0001) during the OFF condition, and by 7.11% (from 17.01+/-6.63 to 15.8+/-7.22; p<0.001) during the ON condition. Nocturnal akinesia improved in all the patients except one. In the 12 patients without motor fluctuations, when cabergoline was added, the UPDRS score improved by 34.4% (from 23.5+/-5.3 to 15.5+/-4.7). This open study shows that dual dopamine agonist therapy can be useful in the symptomatic treatment of patients with early or more advanced Parkinson's disease receiving therapy with or without levodopa.