Zinc supplementation of anorexia nervosa (AN) patients has been reported to increase the weight gain of AN patients in open trials. In this randomized, double-blind, placebo-controlled trial 100 mg of zinc gluconate, or placebo, was given daily to 35 female AN inpatients until they achieved a 10% increase in body mass index (BMI). The rate of increase in BMI of the zinc supplemented group (n = 16) was twice that of the placebo group (n = 19), and this difference was statistically significant (p = .03). The use of zinc supplementation should be considered in the treatment of AN patients.