This study examined whether dietary phosphate (P_i) restriction stimulates an appetite for P_i in the juvenile rat, which normally has a high metabolic P_i demand for growth. Juvenile Wistar rats were placed in individual cages with unrestricted access to tap water and a low (LPD, 0.02% P_i) or normal P_i diet (NPD, 0.6% P_i) for 7 days. On day 8, both groups of rats were given unlimited access to a solution of 0.3 M potassium phosphate water (P_iH₂O) for 8 additional days. Rats fed LPD consumed 70-100% more P_iH₂O then those rats fed NPD (P < 0.001). The increase in P_iH₂O intake resulted in a marked rise in the growth rate of rats fed LPD during days 8-15. A similar P_i intake was inducible after only 2 days of LPD and was associated with significant reductions in both plasma and cerebrospinal fluid (CSF) P_i levels; these levels remained low throughout P_i restriction, despite a significant P_iH₂O intake. Furthermore, the renal adaptation to enhance P_i reabsorption (T_mP_i) during P_i deprivation remained elevated despite enhanced P_iH₂O intake. Replenishment with a high-P_i diet rapidly quenched the P_iH₂O appetite and was associated with restoration of both plasma and CSF P_i levels. These findings suggest that an appetite for P_i can be induced in juvenile rats, perhaps through lowered plasma and CSF P_i levels. This behavioral response may serve as an additional mechanism to maintain an adequate supply of P_i necessary for growth and development of the animal.