The objective of the present study was to establish whether copper (Cu)-deficient rats fed a diet containing fructose as their sole carbohydrate source require more biotin than the recommended 2 mg/kg diet when egg-white serves as the dietary protein.Eighty weanling male Sprague-Dawley rats were randomly divided into 8 groups according to type of dietary carbohydrate (starch or fructose), level of Cu (0.6 micrograms Cu/g diet or 6.0 micrograms Cu/g diet) and level of biotin (2 mg/kg diet or 10 mg/kg diet).Regardless of the level of dietary biotin, Cu-deficient rats fed a fructose-containing diet exhibited growth retardation, anemia, atrophied pancreata, enlarged hearts and similar death rates. The remaining Cu-deficient rats fed fructose were emaciated and sick regardless of dietary biotin levels. The concentration of biotin in serum and biotin content of liver of rats fed fructose were higher than corresponding values from rats fed starch.Cu-deficient rats fed fructose are not deficient in biotin compared to published normal values. Supplementation of 10 mg/biotin/kg diet did not improve morbidity or mortality and therefore was not beneficial.