This experiment was conducted to investigate the effects of particle size and source of calcium supplements on the laying performances for a period of 12 weeks. A total of 240 Single Comb White Leghorn of 39 weeks old were divided into 6 treatments consisted of oystershell (coarse, medium, fine) and limestone (coarse, medium, fine). The results obtained are as follows. 1. Feed consumption was not affected by the particle size and the source of calcium supplements in the laying hen diets. 2. Egg production rate was slightly higher for the layers fed fine particle size and for the limestone fed groups, but the difference was not significant. 3. No significant difference was Found in egg weight, egg shell wt./egg wt./egg shell thickness and calcium content in egg shell, However, slightly improved results were obtained by the birds Fed coarse particle size and by the oystershell fed groups. 4. Soft and shelless egg production, mortality were higher for the layers fed fine particle size and For those fed oystershell than other treatments, but the differences were nat significant. 5. Nutrient utilizability among treatments was not affected by calcium supplements and/or particle sizes. According to the results obtained, the layers fed the oystershell in coarse particle were more adequate for egg shell quality except for the laying performance.