The global audience for software products includes members of different countries, religions, and cultures: people who speak different languages, have different life styles, and have different perceptions and expectations of any given product. A major impediment in interface development is that there is inadequate empirical evidence for the effects of culture in the usability engineering methods used for developing user interfaces. This paper presents a controlled study investigating the effects of culture on the effectiveness of structured interviews in usability testing. The experiment consisted of usability testing of a website with two independent groups of Indian participants by two interviewers; one belonging to the Indian culture and the other to the Anglo-American culture. Participants found more usability problems and made more suggestions to an interviewer who was a member of the same (Indian) culture than to the foreign (Anglo-American) interviewer. The results of the study empirically establish that culture significantly affects the efficacy of structured interviews during international user testing. The implications of this work for usability engineering are discussed.