This study examined the relative anti-Parkinson's disease (PD) tremor potencies of pergolide and pramipexole in people with PD, using a 3-month double-blind cross-over design. Patients were randomly assigned to receive either pergolide and then pramipexole (n=9) or vice versa (n=8). The dose of the respective dopamine agonist was increased according to a titration schedule up to a maximum 1.5 mg t.d.s., with cross-over at 10 weeks. Assessments were performed at baseline, 4, 8 and 12 weeks. The primary outcome measures were the differences in the clinical (rest and postural) tremor scores on pergolide versus pramipexole. Seventeen PD patients (11 females and six males) with a mean age 68.4 years (range: 55-84 years) and a mean disease duration of 3.9 years (range: 2 months to 13 years) participated in the study. Twelve of the patients were taking other anti-parkinsonian medications. Two patients dropped out of the study whilst on pergolide. Fifteen of 16 patients were able to cross-over from one dopamine agonist to the other, without major retitration. There were no significant differences between the effects of the two drugs on the primary outcome measures, suggesting that the anti-PD tremor efficacies of dopaminergic medications are not dependent on differential affinities for dopamine receptor types.