Role of upper gastrointestinal investigations in a screening study for colorectal neoplasia. Should patients with positive faecal occult blood screening tests who are free of colorectal neoplasia undergo upper gastrointestinal investigation? Altogether 16,985 faecal occult blood tests were completed in a group of 18,818 asymptomatic patients (45-75 years) offered screening at two yearly intervals. A total of 447 (2.6%) were positive and underwent large bowel investigations. No neoplastic disease was identified in 283 (63%) of them. Fourteen (5%) also underwent gastroscopy for upper gastrointestinal symptoms, benign conditions were identified in five and a gastric carcinoma in one. No further investigations were instituted in the remaining 269 subjects who have now been followed up for a median period of 5 years (2-8 years). Five have been referred for benign upper gastrointestinal conditions, but none for upper gastrointestinal malignancy. Thirty one subjects have died - one from gastric cancer (a patient who had undergone a previous partial gastrectomy for a duodenal ulcer and who had persistent upper gastrointestinal symptoms). The remaining deaths were unrelated to the upper gastrointestinal tract. Nineteen people who have left the trial area have been monitored for the development of malignant disease; none have presented with upper gastrointestinal malignancy. These data support the view that upper gastrointestinal investigations need not be performed routinely in this group of subjects, but may be reserved for those with relevant symptoms. 