This study investigates the adaptation of English stops into Mandarin Chinese. English stops have a binary [±voice] contrast, whereas Mandarin Chinese stops are distinguished by aspiration. A corpus study based on 720 English loanwords shows that English voiced stops are mapped to the unaspirated stops in Mandarin Chinese while English voiceless stops are mapped to the aspirated stops in Mandarin Chinese, regardless of whether the English stops are aspirated or unaspirated. This finding is in favor of the phonological view on loanword adaptation in that phonemic contrast in the source language is maintained through one-to-one mapping between the source sounds and the loan sounds. However, the English bilabial aspirated stop [ph] is mapped to either the aspirated or unaspirated bilabial stop in Mandarin Chinese. Further, the English velar stop before a high front vowel is mapped to the Mandarin Chinese affricate. Such mappings differ from the general pattern and can be explained by perceptual similarity based on VOT between the source sounds and the loan sounds. We draw a conclusion that both faithful phonological contrast and perceptual similarity work together for the adaptation of English stops into Mandarin Chinese.