In a retrospective study, treatment with lisuride was compared to pergolide in 25 patients with advanced PD in whom the response to levodopa had diminished. Sixteen patients had wearing off and/or ON-OFF phenomena. Lisuride or pergolide, when added to levodopa, resulted in comparable and significant decreases in disability in both ON and OFF periods; pergolide resulted in a greater increase in the number of hours in which patients were ON. Adverse reactions were comparable on both drugs. However, patients who developed an adverse reaction on one drug did not necessarily develop the same reaction on the other drug. Both lisuride and pergolide are effective anti-Parkinson drugs.