Objective: Patient reported outcomes (PROs) play an increasingly important role in pharmaceutical clinical trials. The Food and Drug Administration (FDA) recognizes that interviewer training affects PRO study results. Further, the FDA asserts that implementation of standardized interviewer training can optimize study quality by minimizing inconsistencies in trial conduct. Presently, there is no standard PRO interviewer training method, and many registration trials neglect this important aspect of ensuring quality data. To test the effectiveness of such training, United BioSource Corporation (UBC) analyzed outcomes of PRO interviewer training in a global clinical trial. Methods: United BioSource Corporation worked in conjunction with a pharmaceutical sponsor to develop a training program for an interviewer administered PRO designed to assess symptom severity and resultant distress to patients. Custom training on instrument content, format and administration guidelines was provided to 519 potential interviewers live (70%) at 4 separate investigator meetings (Nashville, Geneva, Kuala Lumpur, Buenos Aires), or via the internet for those unable to attend an IM (30%). Following training, interviewer knowledge was independently assessed using an exam specifically created for that purpose. Results: A total of 519 interviewers completed the training. Seventy-four percent of interviewers had no previous instrument specific experience. A total of 506 (97.5%) demonstrated scale knowledge mastery (80% or greater). As shown by one-way ANOVAs, performance was not affected by nationality, clinical experience, clinical trials experience, or prior experience with the instrument (all F ratios < 1). Conclusion: We report the global delivery of a comprehensive PRO interviewer training package consistent with FDA goals. The study suggests that comprehensive PRO interviewer training is feasible in multinational trials, is effective in live or remote delivery platforms, and results in high levels of demonstrable scale knowledge across a wide range of clinical and research experience levels.