In an optimal design for mixed-mode surveys, be it within a country or across countries, there are three phases that need attention. The first phase is the design phase: it is important to prevent mode measurement effects when designing the study. A richer source of additional data will help to achieve a better estimation of mode effects. After the data are collected, the next two phases are estimating the potential mode measurement effect due to different modes and adjusting for any such bias. Survey modes differ on several dimensions, for instance, interviewer-administered versus self-administered questionnaires and information transmission and communication. The use of well-established and validated constructs and multiquestion scales across countries and modes helps achieving measurement equivalence countries and modes. Mixed-mode designs and mode changes are often implemented for sound methodological reasons. Using a mixed-mode design implies a careful trade-off among coverage, nonresponse, measurement errors, and cost.