Growing lambs were fed diets that just met their requirement for Ca but which supplied either 1 or 3 times their requirement for P and the effects on Ca and P retention and on bone turnover were monitored. Feeding the high P diet had no adverse effect on Ca and P absorption or retention or on bone formation rate. Bone resorption rate was a little higher in lambs fed the high P diet but there were no differences between treatments in plasma parathyroid hormone, 1,25-dihydroxyvitamin D3 or 25-hydroxyvitamin D3 levels or in bone mineral content. It would appear from these results that feeding diets that are rich in P is unlikely to have any adverse effect on skeletal mineralization in the lamb provided that their minimum requirement for Ca is met.