Some patients with Parkinson's disease (PD) and fluctuations of motor response to levodopa therapy may benefit by avoiding proteins during daytime meals, while leaving them unrestricted until bedtime. The acceptance and benefits of a protein redistribution diet (PRD) was studied in 26 PD patients whose fluctuations were refractory to current medications. Only 15 patients (57.2%) were still adhered to the diet 3 months later. Non compliance was more often justified on the basis of the changes in alimentary habits, as a too heavy supper (37%), scanty variation of meals (27%) and difficulties in preparing the diet (18%), rather than do to adverse effects of the diet on PD which occurred in 2 patients (exacerbation of the dyskinesias and lack of effectiveness, respectively). The PRD proved beneficial to 67% of those patients able to keep adhered to it, 4 patients shifting to stable responses. Five diet-benefit patients who performed daily "on-off" charts decreased their mean daily "off" time from 13 to 3 % (p less than 0.05), but "on" time quality remained unimproved by the diet. The PRD introduces a heavy change in dietary habits which is not readily accepted by many PD patients. However, the fact that fluctuations disappeared in one fourth of those able to maintain the diet warrants a closely supervised, short-time trial to identify those in whom benefits override the inconveniences of such new changes in the patient's way of life.