PROOF that more than symptoms are relieved is elusive. But a price and high brow writing may also explain the weak response to strong evidence that a drug may slow the progression of Parkinson's disease. A 10-mg/d dose of deprenyl (selegiline hydrochloride, eldepryl, Somerset Pharmaceuticals, Denville, NJ) on average, nearly doubled the time before functional disability became significant enough that patients could no longer manage their daily routine without levodopa, according to results of the 800-patient Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) study (N Engl J Med.1989;321:1364-1371). Only 25% of patients taking deprenyl with or without alpha-tocopherol (vitamin E) progressed to that point within a year, compared with 44% of those not taking deprenyl. This result prompted researchers in the 28-center, double-blind study to put all subjects—and most patients in the investigators' own Parkinson's clinics-on the drug. Symptomatic improvement could not by itself account for the