OBJECTIVE: The study aimed to investigate whether the degree of postinfectious olfactory loss is reflected in volume of the olfactory bulb (OB). STUDY DESIGN: Retrospective study of 26 patients with postinfectious olfactory loss. MATERIALS AND METHODS: Olfactory function was assessed with the "Sniffin' Sticks" test kit, and the magnetic resonance imaging study focused on OB volume and the olfactory sulcus. RESULTS: The study revealed that 1) OB volume varies with regard to olfactory function, 2) OB volume decreases with duration of olfactory loss, and 3) patients with parosmia had smaller OB volumes than patients who did not report such smell distortions, although their overall olfactory function was not significantly different from each other. CONCLUSION: The study emphasizes that OB volume is a gauge of olfactory function. © 2006 The American Laryngological, Rhinological and Otological Society, Inc.