The governments of the Orléans Monarchy pursued a very active policy in Spanish America. In 1838–9 France fought a brief war with Mexico. From 1838 to 1840 she was engaged in a dispute with Governor Rosas of Buenos Aires which escalated into an attempt to overthrow him. The French Navy played a distinctly un-neutral role during the Argentine siege of Montevideo in the early 1840s. In 1845 France and Britain cooperated in an attempt to impose a peace settlement upon the belligerents in the Río de la Plata. These two powers also seriously considered a plan to block American expansion in 1845 by offering certain guarantees to Texas and Mexico. The French were also involved in several minor disputes — involving New Granada, Chile, and Mexico again – which nearly led to blows. 1 The armed forces of France were in more constant action only in North Africa. Yet French political and economic interests in Spanish America were hardly as important as these activities implied. In fact, French policy was based upon a misconception of the potential importance of their interests. The error was made worse by the nature of the French policy-making process. The aims of this paper are to explain how these erroneous conceptions of French interests were formulated, why they were not rectified, and why it was the French rather than the British, despite their greater interest in Spanish America, who appeared to wave ‘the big stick’ there during this period.