With the aim of continuing the studies carried out by us for the characterization of the fruit of cupuacu (Theobroma grandiflorum), a tree indigenous from Amazonia and of the same family of cocoa (Theobroma cacao), the presence of caffeine, theobromine and theophylline was investigated. The action on cardiac rhythm and central nervous system of these natural alkaloids, belonging to the family of xanthines, is well known. The determination was carried out in the ground raw and roasted cupuacu seeds and in the corresponding powders obtained after pressure. Caffeine, theobromine and theophylline were determined simultaneously by reversed-phase high performance liquid chromatography with spectrophotometric detection. The results obtained on the described by-products of cupuacu seeds were compared with those obtained in the corresponding by-products of cocoa seeds. The by-products of both cupuacu seeds and cocoa seeds were obtained under the same technological conditions.