The study was done on hundred patients with their ages was ranged between six months to 36 months, they were suffering from acute gastroenteritis with variable degree of dehydration. Half of the cases received oral rehydration so0lution with fibres, and the other half received WHO oral rehydration solution. There was significant statistical differences in the gaining weight in the patients received WHO oral rehydration solution in comparison to the gaining weight in patients received oral rehydration solution with fibres. So we recommend the use of WHO oral rehydration solution to rehydrate the patients with acute gastroenteritis accompanied by dehydration