A 22-year-old female patient presented to our hospital complaining of a headache. Evaluation with magnetic resonance imaging (MRI) demonstrated the absence of sphenoid sinus. Agenesis of sphenoid sinus is a rare entity; it Usually occurs with syndromes. A case of sphenoid sinus agenesis without any anomaly or syndrome is reported. (c) 2005 Wiley-Liss, Inc.