The molecular structure of 4'-bromoflavanone (C15HllOzBr) has been determined by X-ray diffraction and refined by full-matrix least-squares methods based on 1636 reflections recorded on a Picker FACS-1 automated diffractometer. The final R-index is 0-052 (weighted R is 0.023). The crystals are monoclinic space group P21/c, with cell dimensions a= 6.636 (4), b = 16.522 (10), and c= 11.739 (7) A, fl= 98.00 (3) °.There are four molecules in the unit cell; the molecules are optically active at C(2) of the pyrone ring. The racemic crystal has a d, l pair packed about a center of symmetry. The bromine substituted phenyl ring is equatorially substituted at C(2) with the phenyl ring rotated so that its plane is approximately perpendicular (105.5 ° with respect to the A-ring) to the mean plane of the remainder of the molecule.