Aims: To test the effects of data collection mode and ethnicity of interviewers on response rates and self-reported alcohol use among second-generation Turks and Moroccans in Rotterdam, The Netherlands. Methods: Two hundred and sixty-nine Turks and 271 Moroccans were interviewed face-to-face, and 475 Turks and 482 Moroccans received a mailed questionnaire. Half of the Turks and Moroccans randomly allocated to the interview mode were ethnically matched to the interviewer; the remainder were allocated to a Dutch interviewer. Results: Turks and Moroccans more often responded to a face-to-face interview than to a mailed questionnaire. No effect of ethnicity of interviewer on response rates was demonstrated. With respect to the effects on alcohol reports, Turks and Moroccans tended to report a higher alcohol use in the mailed survey than in the face-to-face interview. They reported significantly more often excessive drinking in the mail survey than in the face-to-face interviews. Ethnicity of the interviewer resulted in Turks and Moroccans reporting a higher prevalence of alcohol use during the previous 6 months when interviewed by a Dutch interviewer compared with an ethnically matched interviewer. Conclusions: Among second-generation Turks and Moroccans, mail surveys seem most suitable to measure mean and excessive alcohol use. However, interviews held by Dutch interviewers seem to be the most appropriate method to study the prevalence of alcohol use during the previous 6 months.