Objectives. To study the correlation between Sunnybrook and House-Brackmann facial grading systems at different time points during the course of peripheral facial palsy. Study Design. Prospective multicenter trial. Setting. Seventeen otorhinolaryngological centers. Subjects and Methods. Data are part of the Scandinavian Bell's palsy study. The facial function of 1920 patients with peripheral facial palsy was assessed 5397 times with both Sunnybrook and House-Brackmann (H-B) facial grading systems. Grading was done at initial visit, at days 11 to 17 of palsy onset, and at 1 month, 2 months, 3 months, 6 months, and 12 months. Statistical evaluation was by Spearman correlation coefficient and box plot analysis. Results. Spearman correlation coefficient varied from -0.81 to -0.96, with the weakest correlation found at initial visit. Box plot analysis for all assessments revealed that Sunnybrook scores were widely spread over different H-B grades. With 50% of the results closest to the median, Sunnybrook composite scores varied in H-B grades as follows: H-B I, 100; H-B II, 71 to 90; H-B III, 43 to 62; H-B IV, 26 to 43; H-B V, 13 to 25; and H-B VI, 5 to 14. Conclusion. Gradings correlated better in follow-up assessments than at initial visit. As shown by the wide overlap of the grading results, subjective grading systems are only approximate. However, a conversion table for Sunnybrook and H-B gradings was obtained and is included in the article. It can be used for further development of facial grading systems.