The present experiment was conducted over fifty days to determine the effect of supplementing oyster shell flour, limestone flour, meretrix, and commercial marine shell flour, as a source of calcium in the feed upon egg production and egg shell quality of white Leghorn laying hens. The results obtained are as follows: (1) The amount of feed consumed was larger for limestone and commercial marine shell than for others. The hens in the two lots appeared to have consumed more feed to meet the calcium requirement physiologically because the limestone and commercial marine shell were low in their calcium contents. (2) The decrease in body weight was observed for each of the four treatments. The rate of egg production was somewhat low for limestone lot, but this was statistically insignificant. No significant differences among the; four treatments were observed for egg weight. (3) The thickness and breaking strength of egg shell were significantly poor for limestone lot than for other lots. (p$lt;0.01). The correlation between shell thickness and breakness and breaking strength was high (r=0.85). (4) The calcium content of blood serum and of femur was relatively high for meretrix lot, and was low for limestone lot. But none of the differences in calcium contents among the four treatments were statistically significant. The calcium content of blood serum was significantly correlated with rate of egg production (r=0.66), and that of femur was significantly correlated with egg shell thickness (r=-0.60). The determination of ash content of femur showed no significant differences among the four treatments, although the ash content of femur was relatively high for commercial marine shell lot and was low for Limestone lot. (5) The breaking strength of femur showed no significant differences among the four treatments, although the meretrix lot showed considerably high value of ash content. The breaking strength of femur was highly correlated with its ash content (r=0.76, p$lt;0.01), but was only slightly correlated with its calcium content (r=0.44, p$lt;0.05). (6) No significant differences among the four treatments were observed for production cost and net profit per egg. although the limestone lot was somewhat inferior to others due to its low rate of egg production and to large amount of feed consumed.