There is an extensive literature on the problem of translating scales for use across cultures, but very little is published on the problems of conducting qualitative interviews in another language with assistance of an interpreter. The aim of this paper is to describe and discuss threats to validity that arise when conducting qualitative interviews using an interpreter. Ten female student nurses in two cities in Lithuania were interviewed about how they perceived their educational program. All interviews were conducted in English with an interpreter. When using an interpreter to conduct interviews, potential threats to validity arise at various points in the interview process. A threat arises when the researcher, whose first language is Swedish, addresses a question in English to the interpreter, another during the translation by the interpreter from English to Lithuanian, and again when the interpreter translates the interviewee's Lithuanian responses to English. In the last situation, the researcher may not know whether the interpreter has summarized and/or modified the responses. To mitigate these problems, the interpreter should not only have the required linguistic abilities, but also be trained in the research field. The researcher has to be aware of these threats to validity and make efforts to meet and limit their effects.