The effects of selenium deficiency on the responses to Candida albicans infection were examined in mice. When selenium-deficient and selenium-supplemented mice were given i.v. injections of 0.1 ml suspensions of 1 X 10(5) or 5 X 10(4) C. albicans in 0.9% sterile saline, deaths in the selenium-deficient animals started after 2.5-3.5 d compared with 7-8.5 d in the selenium-supplemented animals. Further studies demonstrated that 3 d after an i.v. injection of 1 X 10(5) C. albicans, significantly more of the microorganisms were found in the kidneys (P less than 0.001), livers (P less than 0.025) and spleens (P less than 0.01) of the selenium-deficient mice compared with the same organs of selenium-supplemented animals. Selenium deficiency was also demonstrated to impair the ability of mouse neutrophils to kill C. albicans in in vitro tests. The possible relationships of this defect in function to decreased resistance to C. albicans infection is discussed.