We have tried to experimentally determine what effect castration is going to have on rats bone and on the main mineral bone regulatory hormones. Twenty ovariectomized female rats and their age and weight matched controls were used. Parathormone, calcitonin, osteocalcin and serum calcium levels were determined as well as mineral bone content and head of femur density. Castration produces, in rat, a marked decrease in circulating calcitonin, parathormone (PTH) and bone density, with no changes in mineral bone concentration. Finally, castration produces a slight increase in osteocalcin serum levels although without a statistical value.