The r(alpha), r(0), and r(s) structures of 1,3,5-triazine ((C3N3H3)-C-12-N-14) have been determined in the gas phase by analysis of electron diffraction data and high-resolution FTIR spectra, including those for the isotopomers (C3N3H3)-C-12-N-15, (C3N3H3)-C-13-N-14, (C3N3H3)-C-13-N-15, and (C3N3D3)-C-12-N-14, in solution in liquid crystal solvents by NMR spectroscopy, and by ab initio calculations. Combining gas- and solution-phase data in a single analysis yields a very precise structure, with final parameter values (r(alpha)degrees) r(C-N) 133.68(1) pm, r(C-H) 108.9(2) pm, and angle(CNC) 113.82-(9)degrees. The final structure obtained is also compared with the crystal structure.