In the July 2005 issue, Young and Meyer suggest that the terms “men who have sex with men (MSM)” and “women who have sex with women (WSW)” are used inappropriately to displace information regarding sexual identity.1 While information regarding sexual identity is important, measures of both sexual identity and sexual behavior should routinely be included on population-based surveys and surveys of health risk behaviors to illuminate interactions between identity, behavior, and adverse health outcomes, including sexually transmitted infections. The Bureau of Sexually Transmitted Disease Control at the New York City Department of Health and Mental Hygiene attempts to interview all persons diagnosed and reported with early syphilis to ensure adequate treatment and appropriate notification and treatment of partners. Since January 2004, interviews have included a sexual identity question phrased as it is in the Massachusetts Youth Risk Behavior Survey.2 Respondents are asked, “Which of the following best describes you? Heterosexual (straight), gay or lesbian, bisexual, not sure, none of the above.” In interviews conducted from January 2004 through June 2005, 84% of men with primary or secondary syphilis infection who reported having sex with other men identified themselves as gay; 11% identified as bisexual and only 4% identified as heterosexual. A high degree of concordance between identity and behavior was seen in all racial/ethnic groups. In contrast, large venue-specific3–5 and population-based studies have revealed a very different picture. Among 3000 men sampled for a general population–based survey of health and risk behaviors conducted by the the New York City Department of Health and Mental Hygiene in 2003,6 there was notable discordance between sexual behavior and sexual identity among MSM, 73% of whom self-identified as heterosexual. Heterosexual-identified MSM and gay-identified MSM had different demographic and behavioral characteristics. Sexual identity and behavior information derived from special studies can be useful for targeting case-based interventions; however, when such data are available on a population level, they give case-based data critical context and can be used to guide broader outreach efforts to groups with differing demographic characteristics. Young and Meyer’s suggestion that investigators should capture the full range of identity terms may not be practical for public health practice and research. Instead, we suggest that public health practitioners and researchers strive to adopt a standard means of measurement and nomenclature for sexual behavior and identity. Furthermore, we caution persons collecting such data, including health care providers, not to rely solely on the terms individuals use to describe themselves, as a man who has sex with another man may well report a heterosexual identity. Providers should specifically inquire about the gender of sexual partners when assessing patients’ risk for sexually transmitted infections.