In vitro studies indicates that the constitutents of the drug combination co-trimoxazole are synergistic against Salmonella and effective against shigella isolated from children ill with gastroenteritis. The drug is well absorbed in children with gastroenteritis due to a variety of causes and is distributed, excreted and metabolized in a manner similar to that seen in normal adult volunteers. The drug is tolerated well by children with gastroenteritis even in very high dosages. Despite its in vitro and pharmacokinetic advantages, co-trimoxazole was not any more efficient than any other durg or no therapy in the treatment of salmonella gastroenteritis; it seems to have a role, however, in the treatment of typhoid fever and may be life-saving in patients infected with ampicillin- and chloramphenical-resistant strains. It is also effective in the treatment of shigella gastroenteritis and is recommended where ampicillin-resistant strains are encountered. Its potential usefulenss for the treatment of other bacterial causes of gastroenteritis in children must be evaluated by further controlled therapeutic trials.