English has become the world’s lingua franca and dominant conference language. Consequently, interpreters are increasingly confronted with nonnative speakers whose pronunciation differs from Standard English. Non-native source texts which deviate from familiar acoustic-phonetic patterns make perception more difficult for the interpreter, who, according to Gile’s Effort Models, is forced to devote a considerable part of his processing to the Listening and Analysis Effort. For students and novices in the interpreting profession such situations are particularly difficult to cope with. The paper describes some of the major findings of a study carried out by Dominika Kodrnja (2001) as a diploma thesis under the author’s supervision to demonstrate the detrimental effect of a strong non-native accent on students’ interpreting performance.