Chemical composition and structural characteristics of cacao (Theobroma cacao L.) hull were investigated. Holocellulose, Klason residue, total amino acid, lipid, ash, and glucose contents were 334, 320, 96, 99, 93, and 174 g·㎏^-1, respectively. Other neutral sugars ranged 21-48 g·㎏^-1. ^13C NMR spectrum of the purified polyphenols of cacao hull suggested that the Klason residue is mainly composed of tannin-like materials, together with small amounts of lignin. The results for total amino acid (96g·kg^-1), nitrogen contents of the Klason residue (25g·㎏^-1) and samples treated with various surfactants (21-27 g·㎏^-1), suggested the presence of polyphenol-protein complexes in cacao hull.