The Energy Affinity Index was mentioned at the end of Chapter 3 among the composite indic ators of energy secur ity that does not include geopolit ical vari­ ables. This index quantitatively characterizes other coun tries as having predomi­ nant com petit ive or com plement ary inter ests in the inter na tional energy market in relation to the coun try or group of coun tries under study. The definition, lim­ ita tions and prac tical use of this index for the EU’s energy relations will be pre­ sented in this chapter.