This study was designed to examine the effect of graded levels of cellulose, zinc and copper on tissue mineral levels. Tissue mineral levels were assayed by atomic absorption spectrophotometry in samples collected from a study which involved 12 treatments in a 3 X 2 X 2 factorial arrangement. This study involved three levels of cellulose (0, 8, and 16% of the diet), two levels of Cu (deficient and adequate; 2 and 18 mg/kg of diet, respectively), and two levels of Zn (marginal and abundant; 10 and 120 mg/kg of diet, respectively). Six weanling, male Sprague-Dawley rats were assigned to each treatment and after 9 weeks they were killed. Reductions of tissue Cu content were observed in the serum, liver, tibia and testis of the rats fed the Cu-deficient diets. The Fe content of the tibia and testis was reduced, but that of liver was elevated in the rats fed Cu-deficient diets. Reductions in tibial Zn levels were observed in the rats fed marginal-Zn as compared to those fed the abundant-Zn diets; and in the rats fed Cu-adequate as compared to those fed Cu-deficient diets. Increases in cellulose resulted in increased liver and testicular Cu content only in rats fed the Cu-deficient diets. Additions of cellulose appeared to have no adverse effect on the distribution of Zn, Cu and Fe in tissues which are sensitive to dietary deficiencies. With the exception of rats fed the copper-deficient, marginal zinc diets, the rats fed the other diets demonstrated a small reduction in serum zinc values as cellulose was increased.