The persistence of the kindled seizure state produced during exposure to 5 mg/kg/day lindane was compared to that produced in nonexposed subjects. Persistence was evaluated at intervals of 2 weeks and 2 months. Rats were kindled on corn oil alone or corn oil + lindane until each rat exhibited a fully kindled seizure. Two weeks later subjects were tested for persistence using a crossover design where half the lindane-kindled rats were retested under lindane and the other half under oil. Two months later, subjects were retested again, without further exposure. The results demonstrate that the kindled state during lindane exposure was equally as stable and persistent as that produced under control conditions. This was true even though kindling required about 40% fewer trials with lindane exposure than without. The equivalence of the control and lindane kindled state is an important finding. It suggests that the proconvulsant action of lindane on kindling is not simply an additive one. Rather, lindane appears to directly increase the rte at which the permanent alterations in neuronal connectivity occur which are responsible for kindling expression.