A 3 X 3 X 2 factorial arrangement was employed to test three calcium supplements (oyster shell, limestone and a mined marine source) and three dietary calcium levels (1.75, 2.50, and 3.25%) as completely ground material or as 1/3 ground plus 2/3 hen-size material in cage layer diets. Egg production, feed consumption, feed efficiency, egg weight and egg shell strength were not significantly affected by the source of calcium. Performance was improved with increasing dietary calcium levels. Egg production, feed efficiency and egg shell strength were significantly lower for birds fed diets containing 1.75% calcium as compared to higher levels. Egg weight and feed efficiency were significantly poorer for the birds fed the 2.50% calcium vs. 3.25% calcium diets. Numerically higher egg breaking strengths were found when hens were fed diets containing 3.25% calcium when compared to 2.50% but these values were not statistically different. Calcium source particle size affected only egg shell breaking strength. Feeding the mined marine source as hen-size significantly improved egg shell strength when compared to the ground material. A similar response was observed for both oyster shell and limestone since hen-size calcium supplements significantly improved egg shell strength as compared to ground material when the data for all three sources were pooled.