Objective: The objective of this analysis was to evaluate functional disability in patients with cervical dystonia. Methods: The study consisted of a 10-week, non-randomized, open-label period followed by a 10-week, randomized, double-blind, placebo-controlled period. A total of 170 patients were randomized to receive a physician-determined dose of botulinium toxin type A (BoNT-A) or placebo. Functional disability was measured by patients and physicians using a scale from 0 (no functional disability) to 4 (very severe disability). Functional disability was measured at study visits at weeks 2, 4, 6, 8, and 10 of the randomized, double-blind period of the study. Results: The baseline mean physician-assessed functional disability scores were 1.87 for botulinium toxin and 1.88 for placebo. The mean change in physician-assessed functional disability showed a greater reduction in the BoNT-A group compared with the placebo group at all timepoints, with the difference being significant at weeks 4, 6, and 8 (P=0.029). A higher proportion of patients had a decrease of one grade or more in physician-assessed functional disability in the BoNT-A group at all time periods. The baseline mean patient-assessed functional disability scores were 1.95 in the BoNT-A group and 1.78 in the placebo group. A greater reduction in the mean change of patient-assessed functional disability was seen with BoNT-A compared with placebo at all timepoints. The patient-assessed functional disability between the two groups was significantly different at weeks 2, 6, 8, and 10 (P=0.008). A one grade or greater reduction in patient-assessed functional disability was experienced by a higher proportion of botulinium toxin patients at all timepoints compared with placebo. Rates of adverse events were nearly equivalent between groups (59.1% BoNT-A vs. 58.5% placebo group). Conclusion: Treatment with BoNT-A showed significant and sustained improvements in functional disability when assessed by both the physician and the patient.