Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies derived Dietary Reference Values (DRVs) for phosphorus. The Panel considered data from balance studies, losses of phosphorus from the body and intestinal absorption for possible use in a factorial approach, and studies on phosphorus intake and long-term health outcomes. The Panel concluded that these data were insufficient for setting DRVs for phosphorus. Data on the calcium to phosphorus ratio in bones of healthy adults, adjusted for the proportion of phosphorus found outside bone, and data on whole-body calcium and phosphorus contents in Caucasian adults indicate that the calcium to phosphorus molar ratio in the body ranges from 1.4:1 to 1.9:1. Although the fractional absorption of phosphorus is higher than that of calcium, the Panel considered that the actual amounts of calcium and phosphorus that are available for absorption from the diet cannot be determined; therefore, the whole-body calcium to phosphorus ratio was used to set DRVs. The data were considered insufficient to derive Average Requirements and Population Reference Intakes. Based on the DRVs for calcium and considering a molar calcium to phosphorus ratio of 1.4:1 to 1.9:1, amounts of phosphorus were calculated. The Panel chose the lower bound of this range (a ratio of 1.4:1, which results in a higher phosphorus intake value) for setting an Adequate Intake (AI), taking into account estimated phosphorus intakes in Western countries, which are considerably higher than the values calculated. The AI is 160 mg/day for infants (7–11 months) and between 250 and 640 mg/day for children. For adults, the AI is 550 mg/day. Taking into consideration adaptive changes in phosphorus metabolism that occur during pregnancy and lactation, it was considered that the AI for adults also applies to pregnant and lactating women.