Introduction– A multicentre, randomized, double-blind, placebo-controlled, parallel group study was carried out in 123 patients suffering from never treated (de novo) idiopathic Parkinson's disease (PD). The aim of the study was to confirm the efficiency and safety of α-dihydroergocryptine (α-DHEC) given as monotherapy in the symptomatic treatment of PD. The total score of the Unified Parkinson's Disease Rating Scale (UPDRS) was identified as the efficacy target variable. Patients and methods– Sixty-two patients (32 males, 30 females, mean age±SD 64±10) were randomized to α-dihydroergocryptine and 61 (30 males, 31 females, mean age 63.8±9.1) to placebo. According to the experimental design, a 18-month double-blind phase vs placebo was followed. Two interim analyses were planned both at the 3rd and 12th month of treatment, in order to avoid continuation on placebo, if clear differences between groups were found (stopping criterium: nominal significance level equal to 0.022 in the analysis of the target variable). Analysis of variance was performed both on the per protocol (PP) and intent-to-treat (ITT) sample. Results– The results on the first interim analysis showed significant differences between treatment groups of the UPDRS total score both in the ITT (115 patients, α-DHEC: No. 56; placebo: No. 59; P=0.019) and PP (96 patients, α-DHEC: No. 46; placebo: No. 50; P=0.001) sample, why the trial was stopped. At the time of stopping the trial, 73 patients (α-DHEC: No. 37; placebo: No. 36) had reached the 6-month observation visit; the analysis carried out on this subset of patients confirmed the efficacy of α-dihydroergocryptine in early PD and the correctness of the decision to stop. The incidence of adverse drug reactions (ADR) did not differ between α-dihydroergocryptine and placebo recipients, gastrointestinal complaints being the most frequent. Conclusion– The results indicate that α-dihydroergocryptine is safe and effective in improving symptoms of de novo parkinsonian patients.