The crystal structure of bumetanide has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Bumetanide crystallizes in space group P-1 (#2) with a = 5.00168(4), b = 9.22649(3), c = 19.59924(14) Å, α = 80.7941(5), β = 82.8401(7), γ = 86.8148(7)°, V = 885.268(9) Å3, and Z = 2. The crystal structure is layered with the double layers parallel to the ab plane. The exterior of the layer is composed of hydrocarbon portions of the molecule, both phenyl rings and butyl side chains. The central portion of the bilayer contains the hydrogen-bonding regions, both the carboxylic acid dimers and the hydrogen bonds involving the sulfonamide groups. The molecular conformations of bumetanide in this current triclinic structure and the previously-determined monoclinic polymorph FEDGON are very similar, as are the energies of the two polymorphs. The powder pattern is included in the Powder Diffraction File™ as entry 00-066-1609.