Lexical pitch accents in bimoraic particles of Tokyo Japanese are believed to be deleted when the particles are combined with accented words. Analysis of the Corpus of Spontaneous Japanese revealed, however, there are many cases where particles retain their accent, thereby forming an accentual phrase of their own. Factors that favor accent preservation include semantic properties of particles, inter-accent distance, boundary pitch movements, and, formality of speech. Particles having emphatic and/or limitative meanings, like /sa’e/, /ko’so/ and /no’mi/, are the most probable to retain their accents.