OBJECTIVE: The objective of this study was to determine whether aggressive medical therapy of gastroesophageal reflux disease (GERD) could improve both subjective and objective features of chronic resistant sinusitis (CRS). METHODS: Consecutive patients with CRS underwent assessment of GERD and sinus symptoms, esophageal motility testing, dual-channel esophageal pH testing, and laryngoscopy and nasal endoscopy at baseline. The results were compared to those of a group of GERD patients without sinus problems. The CRS patients alone then received omeprazole 20 mg b.i.d. for 3 months with symptom follow-up at monthly intervals. Laryngoscopy and nasal endoscopy were repeated at 3 months. RESULTS: Eleven patients with CRS and 19 GERD patients participated. Eight CRS patients experienced heartburn at least once weekly. Esophageal manometry and pH test results were similar between the two groups. Nine CRS patients had an abnormal pH test. All 11 CRS patients completed the 3-month course of omeprazole. Individual sinus symptoms (nasal congestion, nasal drainage, sinus pressure, facial headache, malaise) and global satisfaction were modestly improved in 25-89% and 91%, respectively, at 12 wk. Resolution of symptoms occurred infrequently. We identified no baseline variable that could predict symptom improvement. Although laryngoscopy and nasal endoscopy were abnormal in most CRS patients at baseline and improved in some after treatment, these changes did not parallel symptom improvement. CONCLUSION: In this small, prospective, open label study, we demonstrated a high prevalence of GERD in patients with CRS, many of whom experienced modest sinus symptom improvement after using omeprazole b.i.d. for 3 months. These findings warrant further randomized, controlled study in a larger patient population.