Twenty-four weanling male Wistar rats were divided into four groups fed diets containing adequate or deficient levels of selenium (0.5 ppm [+ Se] or < 0.02 ppm [- Se] and protein (15% [+ Pro] or 5% [- Pro]), but adequate levels of all other nutrients for 4 wk to determine the effects of Se deficiency and protein deficiency on tissue Se and glutathione peroxidase (GSHPx) activity in rats. Plasma, heart, liver, and kidney Se and GSHPx were significantly lower in Se-deficient groups in relation to Se-sufficient groups. In Se-deficient groups, Se and GSHPx were significantly higher in - Se - Pro rats in heart, liver, and kidney. Data analysis showed that there were significant interaction effects between dietary Se and protein on Se and GSHPx of rats. It is assumed that under the condition of Se deficiency, a low level of protein may decrease Se and GSHPx utilization, increase GSHPx synthesis, and result in Se redistribution. This could account for high levels of Se and GSHPx in the - Se - Pro rats compared to - Se + Pro rats.