Pentoxifylline pretreatment protects rat gastric mucosa against indomethacin-induced damage. Lipid peroxidation after indomethacin treatment (determined as thiobarbituric acid reactants) was significantly reduced by a single dose of pentoxifylline. The same was true for pentoxifylline administration for 6 days. There is a relationship between reduced lipid peroxidation, decreased number of circulating activated neutrophils and diminished disposition for acute gastric mucosal lesions induced by indomethacin in pentoxifylline-pretreated rats.