This chapter reviews properties and functions of endogenous ionic currents in hippocampal neurones. Currents considered are: Na currents INa(fast) and INa(slow); Ca currents; K currents--delayed rectifier IK(DR), transient IK(A), 'delay' current IK(D) and M current IK(M); inward rectifiers IQ, IK(IR) and ICl(V); Ca-activated currents IK(Ca) (IC and IAHP), ICl(Ca) and Ication(Ca); Na-activated currents; and anoxia-induced currents.