Most drugs are carried from the site of absorption to their intended site of action (target site) by the bloodstream, either dissolved in the serum or bound to plasma proteins. Binding to plasma proteins influences (i.e. limits or favours), drug distribution through the body. Usually it is the unbound drug concentration that determines its pharmacological and toxicological properties. Our ability to design suitable drug candidates depends on our ability to understand the molecular characteristics of drug-protein binding and ideally be able to predict the extent of binding in vivo. Here we review the different approaches that have been used to model and predict the binding of drugs and drug like molecules to plasma proteins in the body.