Background: Aim of the present, unblinded, multicentric, open trial was to compare effects of 3 treatments in patients with olfactory dysfunction. Methods: Treatments included administration of systemic corticosteroids (oral prednisolone), local corticosteroids (mometasone nasal spray), and systemic vitamin B, respectively. A total of 192 patients participated (95 women, 97 men; mean age 56 years). Duration of the smell loss ranged from I to 288 months (average 45 months). Olfactory dysfunction was due to infections of the upper respiratory tract (n = 72), sinunasal disease (n = 19), and posttraumatic olfactory loss (n = 10); the largest portion was classified as idiopathic (n = 85); other causes were rare (n = 6). Results: Following systemic administration of corticosteroids improvement of olfactory function was observed (p