Gastroesophageal reflux (GER) is common among patients with asthma, and it has been speculated that high GER may exacerbate asthma in some. This study was designed to determine if suppression of acid reflux in patients with asthma would improve pulmonary function. A double-blind, placebo-controlled crossover study design was used to determine the effect of GER suppression with omeprazole (20 mg twice daily) on pulmonary function among asthmatic patients with esophagitis. Four of 15 (27%) asthma patients with GER were shown to have a > or = 20% net improvement in pulmonary function (FEV1) after treatment for six weeks with omeprazole. These results indicate that some patients with asthma and GER will have improved pulmonary function when acid GER is treated with omeprazole.