Abstract Two experiments were conducted with commercial strain, White Leghorn laying hens, kept in wire cages, to determine the effect of low dietary phosphorus (P) levels on production characteristics. In experiment 1, rations that contained 0.19, 0.28 or 0.37% available P (AP) were fed to 22 week old hens. The total (TP) and inorganic (IP) levels of these rations were 0.42, 0.51, 0.60% and 0.09, 0.18, 0.27%, respectively. All dietary P levels supported a high rate of egg production during the 140-day trial. Ration treatments did not affect feed consumption, feed efficiency or average egg weight. Mortality, however, was slightly higher for hens fed 0.19% AP. The second experiment utilized 47 week old hens of a different strain. A basal ration containing 0.10% AP (0.30% TP all from plant sources) was used as one ration treatment. Three additional treatments were obtained by including defluorinated rock phosphate in the diet to supply 0.09, 0.18 or 0.27% IP. Egg production by hens fed 0.10% AP decreased markedly within four weeks, while egg production by hens fed 0.19% or more AP (0.09% or more IP) continued at a high rate throughout the 56-day trial. Hens fed 0.10% AP also lost considerable body weight and suffered a relatively high death loss. Feed consumption and femur ash were not affected significantly by dietary P. The results indicated that relatively low dietary P levels can fulfill the laying hen’s requirement for egg production provided that about 0.19% or more AP is present in the ration. To maintain livability, as well, the AP requirement may be at least 0.28%.