We report the long-term clinical responses of 2 parkinsonian patients with severe "on-off" phenomena who have been receiving continuous duodenal levodopa (LD) infusions. The rate of LD infusion needed to keep the patients just "on" declined gradually during the initial 60 days of infusion and then remained constant. Total LD intake declined rapidly during the first several days and gradually for another 60 days, after which it remained stable. Motor fluctuations virtually disappeared in both patients during the time of the day when the pump was in use. This was accompanied by a decline in the plasma LD concentration needed to just maintain the "on" stage in one patient.