J. Walter Thompson (JWT), the leading American advertising agency until the 1970s, established a branch office in Paris in 1927. While many of JWT's worldwide branches became the leading agencies in their respective countries, notably Great Britain and Germany, JWT-Paris foundered from the late 1920s through the early 1960s. This article focuses on the reasons why: cultural clashes between the French and Americans, a regulated and protected French market, anti-Americanism among French businesses, and American condescension and insensitivity. It concludes with an analysis of and the reasons for JWT-Paris's achievement of limited success by the late 1960s.