The present study was carried out to evaluate the effects of feeding lcw- nonphytate-diets, with and without microbial phytase on the productive and reproductive performance. and egg quality of Mamourah laying hens. Two hundred and forty, 21-week-old Mamourah hens were assigned to eight equal experimental groups of 3 replications of 10 birds each, and housed in individual battery cages. Eight isocaloric (ME; 2700 kcallkg) and isonitrogenous (16% CP) experimental diets containing graded levels of nonphytate P (NPP', 0.25, 0.225, 0 20 or 0 175%, equwalent to 100, 90, 80 and 70% of NPP level recommended by NRC 1994 for laying hens) were formulated in the absence or presence of microbial phytase (MP: 500 Ui'kg diet) and given to the birds, from 21 to 45 weeks of age. At 25 weeks of age and onwards, the hens were artificially inseminated twice a week using freshly- collected undiluted semen from cockerels of the same age and strain, which had been fed the control diet. The criteria of reSponse were change in body weight, productive performance (daily feed and NPP intakes, egg production rate, egg weight. daily egg mass and feed conversion ratio), some egg quality traits (egg components and certain parameters of eggshell and interior quality), reproductive performance (egg fertility, hatchability, embryonic mortality and hatch weight of chicks), certain blood parameters (plasma levels of glucose, total lipids, cholesterol, albumin, total calCium and inorganic P as well as activities of plasma alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase). Ash, Ca and P contents of tibia bone and eggshell were also determined. Regardless of dietary MP supplementation, daily NPP intake and plasma inorganic P concentration were directly related to dietary NPP level, whereas all other criteria were not significantly affected Dietary supplemental MP, independent of dietary NPP level, significantly (P5001) Improved eggshell quality. as measured by percent egg shell, egg speCific gravity and shell weight per unit surface area, and significantly (P5001) increased the hatch weight of chicks and plasma alkaline phosphatase activity but had no significant effect on all other parameters. No significant NPP level by MP interactions were observed for all criteria measured. it would be concluded that dietary NPP level can be decreased to 0.175% for caged Ma mourah laying hens, without adversely affecting their productive and reproductive performance or eggshell quality. Even though the results showed that dietary sUpplementation with microbial phytase was dispensable; yet as long as it may concern, it appeared to have a slight beneficial effect on eggshell quality.