Phosphorus utilization in four laying hens has been studied by means of radiophosphorus (P32), which was incorporated into the laying mash as tricalcium phosphate replacing the bone meal in the diet. The results obtained indicate that, for these four hens:1. The phosphorus that was absorbed appeared in the yolk, white, and shell within 24 hr. after feeding.2. The maximum recovery of P32 following a single feeding was within 24 hr. in the case of the shell, 48 to 72 hr. for the white, and 144 hr. (six days) for the yolk.3. A large portion of the unabsorbed phosphorus was excreted within 24 hr. of feeding.4. A considerable quantity of the phosphorus absorbed by the digestive system was found to be stored in the tibiae at least 40 days after feeding.5. The percentage uptake of phosphorus from tricalcium phosphate rose gradually in the egg and became relatively constant in about 14 to 15 days after the first feeding of tricalcium phosphate.