CD44 is an important adhesion molecule that specifically binds hyaluronic acid and regulates cell-cell and cell-matrix interactions. Increasing evidence has indicated that CD44 is assembled in a regulated manner into the membrane-cytoskeletal junction, a process that is mediated by ERM (ezrin/radixin/moesin) proteins. Crystals of a complex between the radixin FERM domain and the C-terminal cytoplasmic region of CD44 have been obtained. The crystal of the radixin FERM domain bound to the CD44 cytoplasmic tail peptide belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 62.70, b = 66.18, c = 86.22 A, and contain one complex in the crystallographic asymmetric unit. An intensity data set was collected to a resolution of 2.1 A.