The purpose of this study is to consider the diplomatic relations of the United States and Mexico during the earlier phases of this last revolutionary period, dealing in particular with the diplomacy of Henry Lane Wilson, Ambassador of the United States to Mexico City. His term of office began in the closing months of the Diaz regime, continued through the administration of Madero, and terminated while the Huerta government was making its unsuccessful bid for diplomatic recognition. During this interval, Wilson's own government also underwent a change of administration. Altogether, it is a turbulent chapter in the history of American diplomacy.