This study will examine the effect of treatment of GERD on mild to moderate OSA. Fifty individuals identified as having mild to moderate OSA (diagnosed by overnight sleep study or PSG) and GERD (confirmed by an esophageal probe) will be enrolled. Both men and women will be included in this study and no “special populations” will be utilized. Subjects will fill out questionnaires to subjectively measure sleepiness, OSA-related symptoms, GERD-related symptoms, and sleep apnea-related quality of life. They will then be randomized to receive either 12 weeks of the proton pump inhibitor lansoprazole (Prevacid) or placebo (twenty five subjects per group). Upon completion of the 12 week trial, subjects will return and the following data will be collected; repeat all of the baseline questionnaires, repeat PSG and repeat pH probe.