This is the first in-depth study of the early trial-and-error experiences of contracting between Japanese and western merchants trading in the Japanese Treaty Ports in the eighteen year period immediately following the opening of the ports in 1859. Fundamental to the equation were the inevitable east-west cultural and legal ambiguities that impacted on the traders. The learning curve for both westerners and Japanese regarding the nature and application of western contracting law was predictably difficult, tortuous and open to constant misunderstanding. Nevertheless, it was within such a framework that the principal benchmarks for trade with Japan were set down and which, in essence, have lasted to the present day.