The concept of net electrophilicity (electroaccepting power relative to electrodonating power) is introduced. It provides expected trends in most cases. A net electrophilicity scale is presented. Various reactivity descriptors for 32 molecules are calculated at the B3LYP/6-311+G(d) level of theory. Profiles of net electrophilicity along the reaction paths of thermoneutral, exothermic, endothermic, and cycloaddition reactions are analyzed. Net electrophilicity often attains its minimum value for a stable state or a favorable reaction.