OBJECTIVE To assess if early deterioration is a negative prognostic factor in Bell's palsy and if prednisolone treatment reduces early progression and enhances recovery. METHODS Data extracted from the randomized, double-blind, placebo-controlled multicenter, Scandinavian Bell's palsy study. METHODS Sixteen tertiary referral centers in Sweden and one in Finland. METHODS A total of 829 patients aged 18 to 75 years with Bell's palsy. METHODS The study design was factorial; 416 patients were given prednisolone, whereas 413 did not receive the drug. Data were analyzed with a modified intention-to-treat principle and the last-observation-carried-forward method. METHODS Facial function was assessed within 72 hours before treatment start, at Days 11 to 17, and at 12 months. Sunnybrook was used as the main facial grading system with complete recovery defined as Sunnybrook 100. RESULTS In 236 (28%) of 829 patients, the palsy deteriorated from baseline to the first follow-up at Days 11 to 17. Complete recovery at 12 months was 45% among subjects with early deterioration compared with 73% in patients with no initial deterioration (p < 0.0001). In the early deterioration group, complete recovery at 12 months was 62% in patients treated with prednisolone and 31% in those not treated (p < 0.0001). CONCLUSIONS Early deterioration in Bell's palsy is a negative prognostic factor for complete recovery at 12 months. Prednisolone given within 72 hours may reduce early progression and improve the outcome of palsy.