This study was performed to determine the effect of isoflavone on bone mineral density and bone mineral content in growing male rats. Twenty male, Sprague-Dawley rats were assigned to groups, that underwent 9 weeks of experi-ental treatment. Animals were assigned to one of two diet groups (casein group or casein supplemented with isoflavones). During 9 week of the study, food consumption was determined every other day through the measurement of total food given subtracting the food uneaten from original amount given. Rats in two experimental groups had similar initial body weights. At the end of experiment, however, the casein group had significantly greater body weights compared to casein supplemented with isoflavones group. It was also observed that the casein group had greater food intake comared to casein supplemented with isoflavones group. The difference in the final body weights of the groups was therefore due to difference in amount of food ingested, but could be due to the effect of isoflavones. Total BMD, spine BMD, and spine BMC per weight and femoral BMD per weight were significantly greater in casein supplemented with isolaones group than casein group. ALP and osteocalcin were significantly greater in the casein-fed group. Crosslink value was significantly lower in the casein supplemented with isoflavones group, All other variables were statistically similar between two groups. Overall, it can be concluded that casein supplemented with isoflavones beneficial for acquisition of bone mineral density and content on growing male rats.