Blood glutathione peroxidase (GSH-Px) levels in 709 normal dromedary camels (442 females and 267 males) were assessed in the Canary Islands. All animals were intensively reared, and three different nutritional systems were evaluated, depending on selenium content of the diet. Mean GSH-Px level in the total population was 288.5+/-157.2 IU x g(-1) Hb. Reference ranges were estimated and enzymatic activities below 51 IU x g(-1) Hb were considered inadequate. GSH-Px activities obtained in females (298.1+/-155.7 IU x g(-1) Hb) were significantly (P = 0.037) higher than in males (272.6+/-157.2 IU x g(-1) Hb). When age groups were compared, only males between 6 and 12 months old exhibited significantly lower mean GSH-Px (P = 0.006) than females. A high correlation (r = 0.88) between serum selenium concentration and blood GSH-Px activity was estimated, and the regression equation was y = 2.5101x + 42.423. Selenium content of the diet above 0.1 mg x kg(-1) DM seems to supply adequate selenium requirements for dromedaries under intensive husbandry.