A programmatic series of studies developed and evaluated the Attitudes toward Transactional Sex Scale (ATTS) to measure adolescents' attitudes toward engaging in a sexual encounter initiated by an older adult offering desired objects such as cell phone, clothes, cash, or car rides in exchange for sex. Qualitative interviews informed the initial item generation followed by a series of studies assessing the psychometric properties of the measure. Study 1 evaluated the ATTS in a sample of 186 Batswana adolescents and assessed the factor structure, item-to-whole correlations, internal consistency, and convergent validity. In Study 2, the ATTS was administered to a cross-validation sample ( = 387). Confirmatory factor analysis, convergent validity, and internal consistency were consistent with the findings from the original sample. Discriminant validity was also assessed in Study 2. A subset of the sample ( = 119) completed the measure on two occasions and yielded satisfactory test-retest reliability. The resulting instrument appears to have sound psychometric properties and can be used to measure adolescents' attitudes toward accepting such adult sexual initiation that are implicated in the disproportionate burden of HIV among adolescents and young adults in sub-Saharan Africa. No existing measure with known psychometric properties has previously been available.