The hippocampus is an important region for our memories. Many researchers have focused especially on the CA3 region of the hippocampus and have proposed many computational models of the CA3. Conventionally, they have mono-functionally modeled this region as autoassociative memory or heteroassociative memory. However, we derive auto- and heteroassociative functions of the CA3 from anatomical findings of recurrent collaterals in CA3 subregions and physiological findings of spike-timing dependent plasticity in dendrites. On the basis of computer simulations, we suggest that the CA3 should be modeled as auto- and heteroassociative memory.