In　recent　years,　many　approaches　have　been　introduced　in　next　generation　(5G)　wireless　cellular　networks　in　response　to　the　demands　for　higher　data　rates　and　broader　coverage.　In　this　paper,　a　novel　downlink　three-dimensional　(3D)　beamforming　scheme　is　proposed　for　the　5G　multiuser　multiple-input　multiple-output　(MU-MIMO)　system.　This　scheme　separates　beams　in　the　so-called　elevation　domain　via　base　station　(BS)　antenna　tilt　assignment,　with　the　objective　of　reducing　inter-user　interference.　The　key　to　this　scheme　is　controlling　the　vertical　radiation　pattern　of　BS　antennas,　which　is　realized　by　more　efficient　use　of　a　two-dimensional　(2D)　planar　antenna　array.　Moreover,　we　give　the　optimal　solution　of　3D　beamforming　to　maximize　the　users　average　data　rate,　including　adjustments　of　the　antenna　array　and　the　corresponding　multiuser　selection　algorithm.　This　can　be　used　as　a　systematic　framework　for　any　given　3D　scenario　to　mitigate　inter-user　interference.　Our　simulation　results　demonstrate　the　performance　benefits　in　terms　of　transmission　rate　in　comparison　with　traditional　schemes.　©　2015　IEEE.