The Affinity Database 'AffinDB' contains affinity data for protein-ligand complexes of the PDB. Its purpose is to provide direct and free access to the experimental affinity of a given complex structure. As of Monday, November 28th, 2005, AffinDB contains 746 affinity values covering 474 different PDB complexes. More than one affinity value may be associated with a single PDB complex, which is most frequently due to multiple references reporting affinity data for the same complex.