The effect of D-mannose and D-glucose on bacteriuria due to Escherichia coli with mannose-sensitive adhesins was investigated in adult male Sprague-Dawley rats undergoing diuresis. Inocula of 10⁵, 10⁷, or 10⁸ bacteria in 0.1 ml of normal saline or 2.5% or 10% D-mannose or D-glucose were injected intravesically and urine was cultured 1, 3, 5, 7 and 9 days later. The levels of bacteriuria on days 1 and 5 were significantly lower in rats inoculated with 10⁵ E. coli and 10% D-mannose than in controls (p<0.05 and="" 0.01="" respectively)="" and="" the="" percentages="" of="" rats="" with="">< 100="" bacteria/ml="" were="" higher="" on="" days="" 1="" and="" 3="">p=0.05 and 0.02 respectively). Bacteriuria was significantly lower in rats inoculated with 10⁷ bacteria and 10% D-mannose than in controls on days 5 and 7 (p<0.01 for="" each="" day)="" and="" the="" percentage="" of="" rats="" with=""><100 bacteria/ml="" was="" higher="" on="" day="" 7="">p=0.01). D-glucose reduced bacteriuria significantly only with a concentration of 10% after instillation of 10⁵ E. coli (p<0.05, day="" 1).="" the="" results="" indicate="" that="" d-mannose="" and="" d-glucose="" can="" significantly="" reduce="" bacteriuria="" within="" 1="" day="" and="" that="" their="" efficacy="" is="" dependent="" upon="" the="" concentration="" of="" both="" saccharide="" and="">