White New Zealander rabbits were tested for erythrocyte-borne reference values of glutathion peroxidase Px activity, with correlations being established between that activity and selenium content of the blood. The average glutathion peroxidase Px activity in untreated clinically intact rabbits was 11.8 K/g Hb. That value doubled following five selenium applications in therapeutic dosage. The values empirically determined were well adapted to normal distribution. Selenium concentrations recorded from organs of control animals were in fair agreement with values established in earlier studies (Wiesner et al., 1978). The correlation coefficient was r = 0.7117 (n = 44, alpha less than 0.001). The equation of regressive straight line Y oder X (ŷ) was ŷ = -5.3 + 59.94x, and that of X over Y (ŷ) was ŷ = 0,27 + 0,0095y, when Y defined the activity of glutathion peroxidase Px and X the selenium level in the blood.