Ongoing studies from this laboratory have demonstrated marked potentiating actions of the sex steroid 17β-estradiol (E 2) on glutamate-induced excitation. In the present study, systemic injection of a physiological dose fo E 2 was demonstrated to augment significantly excitatory responses of cerebellar Purkinje (Pnj) cells to iontophoretic application of the specific excitatory amino acid (eaa) agonists quisqualate and N-methyl-d-aspartate. Potentiation of eaa responses was observed as rapidly as 5–10 min post E 2, and was, in many cases, a persistent, non-decremental effect. These observed long-term actions of E 2 may provide one mechanism for the activating effects of the steroid on sensorimotor function and acitivity.