Magnetic resonance images frequently demonstrate asymmetrical mucosal volume in the nasal area of asymptomatic patients. To further evaluate this phenomenon, sequential MR examinations of the nasal cavity and paranasal sinuses were performed three to four times during a 3 to 8 hours period in ten normal volunteers. The study demonstrated that the mucosal volume changes alternated from side to side during this period in eight volunteers. Changes were also observed within the ethmoid sinuses, nasal septum and nasolacrimal ducts. Awareness of MR findings of nasal cycle may reduce the likehood of inflammatory disease being confused with normal physiologic changes, and also may provide another method in the study of this physiologic phenomenon.