This paper is the second part of the review on opioid receptor ligands and deals with the progress in the field of non-peptide opioid receptor antagonists (starting from the pioneering opiate studies in the early seventies) with particular stress on the last decade accomplishments. As X-ray high resolution structure determination of the ligand-receptor systems for G protein-coupled receptors meets with considerable experimental obstacles, the knowledge about ligand interactions with the membrane-bound receptors traditionally derives from structure-activity studies. Hence, such a concise summary, collecting chemically distinct but pharmalogically relative compounds, may be a convenient information source for any research concerning ligand-opioid receptor binding or rational drug design.