OBJECTIVES: Botulinum Toxin Type-A (BoNTA) is approved for many therapeutic indications in Canada, including blepharospasm, 7th cranial nerve disorders, cervical dystonia, focal spasticity, cerebral palsy, and hyperhidrosis.  Unfortunately, little is known about the impact of treatment on health utility. The objective of the ongoing national MOBILITY study is to measure the impact of BoNTA on health utility. METHODS: Phase IV prospective observational cohort study in patients receiving BoNTA for approved therapeutic indications in Canada. Physical component scores (PCS), and mental component scores (MCS) are derived from self-reported SF-12v2 at baseline, week 4 and subsequent clinic visits. Health utility is then measured using the SF-6D scoring programme. In this interim analysis continuous data were analyzed by student's t-test and dichotomous data by Chi-square test. RESULTS: To date 917 patients have been enrolled at 40 clinical sites with a 94.5% retention rate. 69.7% of patients returned the week 4 survey and data from 608 individuals were included in the analysis (526 were receiving ongoing BOTOX® treatment at baseline; 82 were BoNTA-naïve). Significant differences were detected in self-reported SF-6D scores between baseline and week 4 in the analysis of continuous (p=0.05) and dichotomized data (p=0.0001), and between baseline and week 4 in the analysis of continuous MCS data (p=0.03). Among BoNTA-naïve patients, there was a statistically significant difference in SF-6D scores between baseline and week 4 (p=0.03 for continuous data; p=0.018 for dichotomized data). There were no statistical significant changes in the SF-6D scores for patients receiving on-going treatment. CONCLUSIONS: This interim analysis from a large ongoing national study shows that significant improvements in health utility are obtained in patients receiving BoNTA for therapeutic indications. Health utility benefit was most pronounced in BoNTA-naive patients as evidenced by week 4 MCS scores (the expected peak effect window). Further recruitment and long term follow-up and analyses are ongoing.