OBJECTIVE: The aim of this study was to estimate the value of work time and productivity loss because of peptic ulcer disease (PUD) and gastroesophageal reflux disease (GERD). METHODS: A total of 300 adult members of Northern California Kaiser Permanente Medical Care Program with outpatient diagnoses of PUD or GERD were randomly selected for a record review to confirm diagnosis. A telephone survey was conducted soliciting information about work loss because of their disease. Reported work losses were valued at self-reported hourly wage to derive work loss costs. A total of 117 PUD and 102 GERD patients participated. RESULTS: About 75% of each sample was employed full-time or part-time. In all, 42% of potentially working PUD patients and 41% of GERD patients reported some lost work productivity because of their disease. The average loss (per person working) was $606 for PUD and $237 for GERD over a 3-month period. Reduced productivity while at work and part-time work because of the disease were the most costly productivity losses for PUD, whereas time off for physician visits and reduced productivity while at work were the most costly losses for GERD. CONCLUSIONS: Work loss costs for patients with PUD and GERD may be nearly as large as direct medical care costs, and are consistent with the more acute nature of PUD and the chronic pattern of GERD. The work losses resulting from these diseases are large enough to warrant consideration in guideline development and policy decisions for patients with PUD and GERD.