The specific binding of L-[3H]glutamate to hippocampal synaptic membranes was examined in rats kindled by tetanic stimulation of the angular bundle. One day after the last of a minimum of 3 class 4 kindled seizures, the binding of L-[3H]glutamate to a quisqualate-sensitive site (GLU A) was about 40% greater than in electrode-implanted unstimulated controls. Saturation binding data indicated an increase in the maximum density of GLU A binding sites with no change in their affinity for L-glutamate. No such increase was detected 28 days after the last kindled seizure, although the animals were still kindled. Radioligand binding to a site that is much less sensitive to quisqualate (GLU B) was unaffected by kindling stimulation. These observations suggest that an increase in GLU A binding sites could be involved in the induction, but not in the maintenance, of the kindled state.