English has won the battle for paramount world language. It is the lan-guage used by the majority of the world's scientists，it is the language of the Internet，and most of the information stored throughout the globe on computers is in English. Its widespread use has resulted in the existence of many varieties，but most of these can be conveniently grouped into one of the two major ‘families' : British English and American English. In Japan，learners are exposed to both kinds，and my experiences as a language teacher here have prompted me to examine the differences between the two. The paper first of all investigates some commonly held attitudes and prejudices towards British and American English. After a brief look at the history of the English language and how the two varieties came to be different，the main differences between the two forms (of vocabulary，spelling，pronunciation，and grammar) are examined. The pedagogical implications of these differences，whether fact or prejudiced opinion，are then considered.