We used a visual lexical decision task to explore control processes in proficient German–English bilinguals. Participants pressed a “yes” button if the letter string was a word in English and a “no” button if it was not. Our critical stimuli were interlingual homographs such as the low-frequency English word TAG. In German, TAG means “day” and is a relatively high frequency word. Overall, our participants responded more slowly to an interlingual homograph than to a control word matched to its English frequency. As we expected, the size of this interference effect depended on various factors. First, including “pure” German words in the stimulus list increased interference. However, participants were able to reduce the degree of interference over time even in the presence of such words. Second, in the absence of pure German words, informing participants about the presence of interlingual homographs from the start of the experimental trials allowed them to reduce interference. We examined the locus of these control effects by analysing carry-over, i.e., reaction times on word trials immediately following an interlingual homograph or its matched control. We inferred from the patterns of interference and carry-over that the primary locus for reducing interference is external to the bilingual lexico-semantic system. We consider the implications of these data for theories of control.