Glutathione is ubiquitous in eucaryotic cells and is implicated in many cellular functions. Release of reduced and oxidized glutathione (GSH and GSSG) into the plasma and the ratio of GSH/GSSG are considered a reliable index to evaluate the status of oxidative stress in biological systems. As storage temperatures and time periods have not been studied and discussed, we evaluated the effects of storage period and temperatures on the stability of GSH in blood samples by an automated capillary electropherograph system. After two-way ANOVA analysis, the result indicated that there were statistical significance between the GSH status and the storage period, and the GSH status and the preserved temperature as well. However, there was no statistical significance between samples with EDTA or with EDTA-NaF added as anticoagulant. Furthermore, no matter which freezing temperature (-20°C or -80°C) was used for storing the samples, the concentration of total GSH was quite consistent over the course of the study. We suggest that the alteration of the GSH status at room temperature should be due to not only the autoxidation of GSH but also the enzyme-catalyzed degradation of GSH and GSSG.