This article analyses the political factors that led the Argentinian government of president Nestor Kirchner to reduce exports of natural gas to Chile and increase its price through new export taxes. First, the political and economic preconditions that might explain these decisions are examined in detail, secondly the natural gas industry in Chile and Argentina is considered, to be followed by an analysis of policies pursued by the Chilean presidents Ricardo Lagos and Michelle Bachelet in order this problem, which has had significant economic impact upon the Chilean economy and its public opinion and which are considered in the final section of the article. The article shows the influence of national factors in decisions affecting foreign policy, which contributes to explain president's Kirchner's politics.