A major impediment in global user interface development is that there is inadequate empirical evidence for the effects of culture in the usability engineering methods used for developing these global user interfaces. This paper presents a controlled study investigating the effects of culture on the effectiveness of structured interviews in international usability evaluation. The experiment consisted of a usability evaluation of a website with two independent groups of Indian participants. Each group had a different interviewer; one belonging to the Indian culture and the other to the Anglo-American culture. The results show that 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.