The aim of this study was to determine seizure-induced oxidative stress by measuring hippocampal glutathione (GSH) and glutathione disulfide (GSSG) levels in tissue and mitochondria. Kainate-induced status epilepticus (SE) in rats resulted in a time-dependent decrease of GSH/GSSG ratios in both hippocampal tissue and mitochondria. However, changes in GSH/GSSG ratios were more dramatic in the mitochondrial fractions compared to hippocampal tissue. This was accompanied by a mild increase in glutathione peroxidase activity and a decrease in glutathione reductase activity in hippocampal tissue and mitochondria, respectively. Since coenzyme A (CoASH) and its disulfide with GSH (CoASSG) are primarily compartmentalized within mitochondria, their measurement in tissue was undertaken to overcome problems associated with GSH/GSSG measurement following subcellular fractionation. Hippocampal tissue CoASH/CoASSG ratios were decreased following kainate-induced SE, the time course and magnitude of change paralleling mitochondrial GSH/GSSG levels. Cysteine, a rate-limiting precursor of glutathione was decreased following kainate administration in both hippocampal tissue and mitochondrial fractions. Together these changes in altered redox status provide further evidence for seizure-induced mitochondrial oxidative stress.