Atrophic gastritis increases the risk of developing gastro-intestinal tumours. An impaired barrier function of the gastric mucosa could contribute to this risk. The absorption of polyethylene glycols (molecular weights 414-766), expressed as recovery in 6-hour urine, was studied both after oral and duodenal loads in patients with atrophic gastritis (n = 18) and compared with controls without gastritis (n = 9). The patients had a higher absorption after oral than after duodenal load for molecular weights 502-546. The differences in absorption after oral and duodenal loads were correlated with the severity of the atrophy in the antrum. No differences were found in the controls. Absorption after the duodenal load did not differ between the study groups. The increased gastric absoφtion of polyethylene glycols in patients with atrophic gastritis may be caused by a permeability disturbance of the gastric mucosa