This paper seeks to answer the question of how the absence of anonymity affects the quality of responses to survey questions regarding sensitive personal issues, or issues that if exposed, could put an individual respondent at risk. An experiment was conducted in a population of young adult males entering a military workforce to assess whether the presence or absence of anonymity within a confidential survey would influence disclosure of rates of alcohol, tobacco, and other drug use. Confidentiality in surveys has been described as “an ethical commitment not to release results in a way that any individual’s responses can be identified as their own. Only when the sponsor cannot identify each person’s response, even momentarily, is it appropriate to promise that a response if anonymous.” A review of the literature comparing modes of survey administration indicates that self-reported alcohol or drug use varies in accuracy depending on how questions are administered. In this study, data were obtained from 1,811 male entrants into a branch of the U.S. military using self-administered questionnaires. Identifier codes were visible on the covers of 1,507 of the instruments (the confidential group) and absent on 304 instruments (the anonymous group). Response rates of 93 percent and 94 percent were obtained for the confidential group and the anonymous group, respectively. Outcome measures included a variety of self-reports on alcohol and other drug use in the year preceding entry to basic training. In addition, cigarette consumption was measured with questions regarding the frequency and quantity of cigarettes smoked in the 30 days prior to entering basic training. Results of the analysis indicate that for quantity and frequency of alcohol consumption, responses from the two groups did not differ significantly. In addition, the differences were non-significant between the two groups for quantity and frequency of cigarette use. For other drug consumption there was no significant difference between the confidential group and the anonymous group. These findings indicate that the lack of total anonymity did not appear to impede the same kind of self-reports of alcohol and drug consumption as those given by the respondents in the anonymous group. These study results support the belief that the presence or absence of identifiers does not make much of a difference if respondents are convinced that the data will be kept confidential. On the other hand, if respondents do not trust the logistics of the survey, they will hesitate to give entirely truthful responses to sensitive questions even if the identifier is left off. 14 references,4 tables, and author note