A study was conducted to determine the effect of selenium supplementation on the performance, selenium status, digestive enzyme activity, and nutrient digestability of selenium-deficient, weanling pigs. At birth, 97 pigs from sows fed a vitamin E-selenium-deficient diet were divided into two groups. One group was injected with 100 IU dl-(alpha)-tocopherol acetate to ascertain the effect on pre-weaning survival. At 3 weeks of age, 72 pigs were weaned and individually fed one of five experimental diets for 4 weeks. The basal diet was a semi-purified, Torula yeast diet deficient in selenium and supplemented with 100 IU dl-(alpha)-tocopherol acetate per kilogram of diet. Treatments were the basal diet supplemented with 0, .025, .050, .075, or .10 ppm selenium as selenious acid. Pigs were weighed, bled, and feed intake was measured weekly. Pigs were killed at the end of the experiment and the pancreases were removed;Percent pre-weaning survival was significantly higher for the vitamin E-injected group compared to the untreated group (90% vs. 70%). After weaning, five pigs receiving no supplemental selenium and one pig receiving .025 ppm supplemental selenium died within the first 2 weeks. In five of these, autopsy revealed gross and microscopic lesions in liver and heart typical of those observed in vitamin E-selenium deficiency. Selenium supplementation had no significant effect on average daily gain (ADG), average daily feed intake (ADF), or feed to gain ratio (F:G). There was a significant linear increase in these performance parameters, regardless of treatment, as time on experiment increased. As a group, unsupplemented pigs had poorer ADG, ADF, and F:G than supplemented pigs, but the difference was not significant. An increase in supplemental selenium and time on experiment produced a significant linear increase in serum selenium concentration and a significant linear and quadratic increase in serum glutathione peroxidase (GSH-Px) activity. A significant treatment by time interaction was observed for serum selenium and GSH-Px activity. With time on experiment, the level of serum selenium and GSH-Px in unsupplemented pigs declined while increasing in supplemented pigs. A significant correlation (r = .81) between serum selenium concentration and GSH-Px activity was observed;Supplemental selenium did not affect the weight or protein content of the pancreas. Selenium concentration of pancreatic tissue increased linearly and quadratically in response to increasing selenium supplementation. The logarithm of pancreatic selenium concentration increased linearly in response to increased selenium supplementation. A significant correlation (r = .35) between selenium concentration and GSH-Px activity of the pancreatic tissue was observed. Selenium supplementation did not affect the activity of trypsin, chymotrypsin, (alpha)-amylase, or lipase in pancreatic tissue. The activity of these enzymes was lower in the unsupplemented pigs than in the supplemented pigs but the difference was not significant. There was a significant linear improvement in apparent digestability of dry matter and nitrogen as selenium supplementation increased. There was no significant treatment effect on apparent digestibility of ether extract. A significant effect of time on experiment was observed for apparent digestibility of dry matter, nitrogen, and ether extract regardless of treatment. The treatment by time interaction was not significant.