A novel application of the Gini coefficient for expressing selectivity of kinase inhibitors against a panel of kinases is proposed. This has been illustrated using single-point inhibition data for 40 commercially available kinase inhibitors screened against 85 kinases. Nonselective inhibitors are characterized by Gini values close to zero (Staurosporine, Gini 0.150). Highly selective compounds exhibit Gini values close to 1 (PD184352 Gini 0.905). The relative selectivity of inhibitors does not depend on the ATP concentration.