While it is well-established that ranitidine 150 mg/day is effective in preventing recurrence and complications of duodenal ulcer, the economic impact of maintenance therapy is unknown. Socio-economic data, allowing to calculate the costs and cost-effectiveness ratio of intermittent and maintenance therapy, were prospectively obtained from a therapeutic trial in 399 duodenal ulcer patients (Mignon et al, Gastroenterol Clin Biol 1990;14:732-8). Visits and endoscopy investigations, work days lost, duration of hospital stay and drug consumption were recorded in both placebo (n = 202) and ranitidine (n = 197) groups. Each source of expenditure was evaluated using current fares and sales prices, from the point of view of both the collectivity and the French Health Care System. The costs of ranitidine strategy were less than the costs of placebo strategy, for the collectivity (2,031 and 2,823 FF per patient for one year, respectively) as well as for the French Health Care System (1,541 and 2,426 FF per patient per year, respectively). In the ranitidine group, expenditures were principally due to the drug (71%) and endoscopy investigation (24%). In the placebo group, endoscopy and hospital stay accounted for 50 and 39% of the expenses, respectively. The latter were due to the occurrence of complications in the placebo group. Sensitivity analysis disclosed that the results were unsensitive to the variations in cost hypotheses of the main expenditure sources. Cost/effectiveness analysis defined as cost per patient successfully treated showed that the cost of a "ranitidine strategy" was 2-3 times less than a "placebo strategy". Maintenance therapy for duodenal ulcer with ranitidine 150 mg/day for one year is less expensive and more cost-effective than intermittent treatment.