We investigated the influences of phonological similarity on the time course of spoken word processing in Mandarin Chinese. Event related potentials were recorded while adult native speakers of Mandarin ("N" = 19) judged whether auditory words matched or mismatched visually presented pictures. Mismatching words were of the following nature: segmental (e.g., picture: "hua1" "flower"; sound: "hua4" "painting"); cohort (e.g., picture: "hua1" "flower"; sound: "hui1" "gray"); rhyme (e.g., picture: "hua1" "flower"; sound: "gua1" "melon"); tonal (e.g., picture: "hua1" "flower"; sound: "jing1" "whale"); unrelated (e.g., picture: "hua1" "flower"; sound: "lang2" "wolf"). Expectancy violations in the segmental condition showed an early-going modulation of components (starting at 250 ms post-stimulus onset), suggesting that listeners used tonal information to constrain word recognition as soon as it became available, just like they did with phonemic information in the cohort condition. However, effects were less persistent and more left-lateralized in the segmental than cohort condition, suggesting dissociable cognitive processes underlie access to tonal versus phonemic information. Cohort versus rhyme mismatches showed distinct patterns of modulation which were very similar to what has been observed in English, suggesting onsets and rimes are weighted similarly across the two languages. Last, we did not observe effects for whole-syllable mismatches above and beyond those for mismatches in individual components, suggesting the syllable does not merit a special status in Mandarin spoken word recognition. These results are discussed with respect to modifications needed for existing models to accommodate the tonal languages spoken by a large proportion of the world's speakers. (Contains 4 tables and 3 figures.)