This study was carried out to investigate the effects of diverse dietary Ca levels and to determine whether bone mineral metabolism is influenced by the arnount of dietary Ca when given a choice of diets containing various levels of Ca. Forty Hy-line brown laying hens housed in separate cages were fed self-selected Ca diets. Birds were allowed a 7-day adaptation period followed by an 8-day collection period. Feed and water were available for ad libitum consumption. Eggs and excreta were collected at 6-h intervals during the day for mineral analysis. The Ca contents in excreta and retained Ca in the body on egg forming day were proportional to the amount of daily Ca intake. The retained Ca in the body were 0.97 g in control and 1.24~1.74 g in self-selected groups, respectively. Daily Ca contents (%) in tibial cortex were not consistent with feeding time intervals. The Ca content in tibial medulla in control group was lower than those of self-selected feeding groups(P<.05). The medullary Ca content in all treatment groups increased from 10:00 to 16:00 in a day. Ca content in plasma was low between 10:00 and 16:00 and was high between 22:00 and 04:00 in the following day.