The assessment of mean cost of upper GI endoscopy is of critical importance if one wants to perform pharmacoeconomic studies, especially in peptic ulcer disease (PUD). The aim of this work was to calculate such costs, based on an inquiry conducted in December 1991 in a representative sampling of 94 French gastroenterologists (GEs) (i.e. 4.3% of the whole population). Thirty-nine percent of GEs work in their office; 25% work in private and 26% in public hospitals. GEs performed 70 +/- 5 (mean +/- SEM) upper GI endoscopies per month. Fifty-nine % are performed to investigate epigastric pain; PUD was found in nearly one patient out of four. Fifteen % of the endoscopies were performed for follow-up of PUD. Upper GI endoscopy modalities varied greatly according to whether performed in GEs' office, private or public hospital. The proportion of investigations performed with biopsies was 66, 71 and 50%, respectively. Neuroleptanalgesia (or general anesthesia), was performed in 8, 49 and 4% of cases, respectively, and a 24-hour hospitalization was required in 0, 7 and 2% of cases, respectively. Sources of expenditure were evaluated according to the current fares of the French Health Care System (for GEs' office and private hospitals) and to real costs (for public hospitals). Taking into account the differences in place and modalities of realization, mean cost of upper GI endoscopy was evaluated at 1,084 FF. This cost could be used in future cost or cost/effectiveness studies of diagnostic or therapeutic strategies.