Weaning mice were supplied drinking water containing Rb1 or Rg1 0.125 or 0.25 mg.ml-1 for 4 weeks. Rb1 (28.6 and 56.1 mg.kg-1) and Rg1 (27.4 and 53.9 mg.kg-1) were found to accelerate young mice body and brain development as well as facilitate memory acquisition in step down and step through avoidance response tests. With the technique of quantitative measurement synapses, we found for the first time that Rb1 and Rg1 administration for 4 weeks can increase synapse number in the hippocampal CA3 region of mice. This is the morphological basis for explaining Rb1 and Rg1 induced facilitation of learning and memory.