The majority of pharmaceutically relevant drug targets cluster into densely populated target families, thus offering a novel approach that complements the currently favoured screening paradigm in medicinal chemistry. This approach uses a privileged structure concept whereby molecular masterkeys are developed that account for a target family wide structural or functional commonality. Numerous lead compounds, based on multipurpose privileged structures, can be generated that address a variety of targets from a gene family of interest, irrespective of therapeutic area. Several different interpretations of the privileged structure concept will be highlighted, with a strong emphasis on the most stringent application: the optimization of a molecular masterkey for a distinct target family of interest.