Headache associated with acute sinusitis is a well-recognized entity; the diagnosis is easily made due to the associated nasal and sinus symptoms. However, the phenomenon of referred headache from chronic sinusitis or intranasal abnormalities or both without upper respiratory symptoms is not well understood. Only recently have the nasal and sinus cavities been adequately visualized by both the human eye and radiographic techniques; a fact that may account for the historic neglect in considering this region a factor in headache etiology. Modern techniques employed in the workup of sinusitis, namely the use of rigid nasal endoscopes and coronal-plane CT scanning, have greatly enhanced the clinician's ability to evaluate and diagnose pathology in this area. This report describes a series of patients presenting with various primary headache syndromes without significant nasal or sinus symptoms who failed to respond to conventional antiheadache therapy. On nasal endoscopic and coronal CT examinations, various intranasal and sinus abnormalities were found (either anatomic variations or subclinical inflammation). Medical and/or surgical therapy addressing the sinonasal pathology resulted in improvement in every case, ranging from decreased severity of attacks to total resolution of headaches. A model explaining the possible mechanism of referred vascular-type headache from sinus and nasal origin is proposed.