Objective: To examine changes in quality of life (QOL) and global clinical status after 30 days of adjunctive treatment with tolcapone, a reversible inhibitor of catechol-O-methyltransferase, in patients with fluctuating Parkinson's disease. Methods: This 30-day, multicenter, open-label, community-based study enrolled fluctuating Parkinson's disease patients to receive tolcapone 100 mg TID as an adjunct to levodopa/carbidopa. The primary end point was QOL change assessed using the Parkinson's Disease Questionnaire (PDQ)-8. Clinical change was assessed using the investigator-rated Clinical Global Impression of Improvement Scale (CGI-I). Results: Fifty-six physicians enrolled 202 patients; 138 (68%) were ≥65 years of age and 116 (57%) had Parkinson's disease for ≥5 years. The mean PDQ-8 total score improved from 42.1 to 34.8 after 30 days of tolcapone (P<.0001). Sixty-nine percent of patients improved on the CGI-I. Physicians planned to continue tolcapone beyond the 30 days in 72%, most commonly because of positive changes in motor function and overall general improvement. No patient discontinued because of liver adverse events. Conclusions: Adjunctive tolcapone treatment was associated with statistically significant improvement in QOL in fluctuating Parkinson's disease patients. A majority of patients experienced clinical benefits and continued treatment beyond the end of this study. No liver-related adverse events were reported. © MBL Communications Inc.