Measurement of sexual behaviors is typically reliant on retrospective self-reports of behaviors. Historically, self-reported sexual behavior data were primarily collected through face-to-face interviews or paper-and-pencil questionnaires, as these were the only modes of inquiry available. In recent decades, technological innovations such as telephones, computers, and the Internet have expanded the self-report inquiry modes available. The addition of these new inquiry modes further complicates the ability of sex researchers to evaluate the quality of research results and compare findings across studies. Self-report sexual behavior data are vulnerable to participation biases, as well as to sources of bias in individual responses, such as recollection and social desirability bias. This is true regardless of the inquiry mode being used, but some modes may be more vulnerable to bias than others. This review examines the available research regarding self-report sexual behavior research, inquiry mode, and relative bias across modes. The review also provides recommendations for advancing the current understanding of inquiry mode effects within sexual behavior research. Specifically, by shifting the focus away from evaluating specific modes of inquiry toward examination of factors common across all modes, researchers will be better able to interpret existing research and improve the designs of future studies as well.