We report on a longitudinal investigation of the realization of English focus by 19 Mandarin-speaking International Teaching Assistants (ITAs). Participants read passages containing contrastive information (e.g., The price of a train ticket is twenty dollars, while the price of a bus ticket is eleven dollars), and then responded to the experimenter’s questions (Is the price of a bus ticket twenty dollars?). ITAs were tested within a month of their arrival in the US, and again at the end of their first semester. Overall, the productions of ITAs at both points in time were judged as less natural by native English listeners than the productions of the native speakers of English, though the naturalness of some ITA productions improved at the second sampling. Acoustic analyses of the ITA productions and comparison with the productions of 18 native English speakers revealed a good deal of interspeaker variability in the ITA productions, with several different patterns associated with the “unnatural” productions: (a) failure to accent the focused element; (b) failure to deaccent the word following the focused element; and (c) failure to align the accent with the stressed syllable of the focused word, with the entire focused word spoken on high pitch.