Phosphate is an essential component of life and must be actively transported into cells against its electrochemical gradient. In vertebrates, two unrelated families of Na⁺-dependent P_i transporters carry out this task. Remarkably, the two families transport different P_i species: whereas type II Na⁺/P_i cotransporters (SCL34) prefer divalent HPO₄^2-, type III Na⁺/P_i cotransporters (SLC20) transport monovalent H₂PO₄^-. The SCL34 family comprises both electrogenic and electroneutral members that are expressed in various epithelia and other polarized cells. Through regulated activity in apical membranes of the gut and kidney, they maintain body P_i homeostasis, and in salivary and mammary glands, liver and testes they play a role in modulating the P_i content of luminal fluids. The two SLC20 family members PiT-1 and PiT-2 are electrogenic and ubiquitously expressed and may serve a housekeeping role for cell P_i homeostasis, however also more specific roles are emerging for these transporters in, for example, bone mineralization. In this review, we focus on recent advances in the characterization of the transport kinetics, structure-function relations and physiological implications of having two distinct Na⁺/P_i cotransporter families.