1. We have reported previously that instant coffee contains ligands for opiate receptors with characteristics similar to those of opiate antagonists. 2. A concentrate of receptor-active ligands from instant coffee was prepared by serial treatments involving Amberlite XAD-2, flash chromatography and gel permeation chromatography. 3. Examination of the final concentrate by GC-MS showed the presence of a number of isomeric (iso)feruloylquinic acid lactones. 4. It is suggested that the synthesis and biological testing of each quinide isomer will establish which is responsible for the opiate receptor activity of instant coffee.