The analytical, intra-individual and inter-individual variations as well as the best storage conditions were determined for erythrocyte glutathione, and the reference values were established. A total of 396 apparently healthy people, 206 male and 190 female, were randomly selected from villages and cities of the southern part of Turkey. The distribution was Gaussian and no significant difference was observed between the male and the female subjects. The mean (standard deviation) of the population investigated for glutathione was 6.9 (1.0) mu mol/gHb. The analytical, intra-individual and inter-individual variations were assessed in 20 apparently healthy subjects and were found to be 4.63%, 13.67% and 11.16%, respectively. Whole blood stored at -70 degrees C for up to 10 days was shown to be the best storage condition for erythrocyte glutathione determination. The results of the index of individuality showed that glutathione reference values could be used for diagnostic purposes. Copyright (C) 1996 Elsevier Science B.V.