Emperor Qianlong of the Qing dynasty celebrated his eightieth birthday in 1790, for which Vietnam, Korea, the Ryūkyū Islands, Burma, and Mongolia sent delegates to the imperial summer resort at Chengde 承德 to pay homage. Curiously, the Annamese (or, Vietnamese) king NguyễnQuangBình (阮 光平), who had just defeated the Qing army, offered to appear in Qing costume and kowtow to the Qing emperor. The unusual act pleased Emperor Qianlong and infuriated the Korean delegates. What did costume and ceremonial mean in the context of the East Asian political and cultural order? Why did the British embassy to China led by Lord Macartney three years later cause friction with regards to sartorial and ceremonial manners? This lecture will address these questions.