1. Bovine parathyroid hormone at a concentration of 1 unit/ml caused an immediate transient uptake of calcium from the bathing medium by 5-day-old mouse calvaria in tissue culture.
2. The uptake of calcium by bone was followed by the release of calcium into the medium over the subsequent 3–4 h.
3. The results support the conclusion that the primary action of the hormone on calcium transport in bone is to cause an increase in the intracellular concentration of calcium before producing the characteristic release of calcium from bone.