The Yomiuri Shimbun introduced dual-frame RDD surveys of landline and cell-phone users for monthly public-opinion surveys. To improve the survey methods, this study investigated experimental dual-frame RDD surveys. The results show that cell-phone surveys are a feasible method for use in Japan, improve the coverage of telephone surveys, effectively reach young respondents, and produce data of adequate quality. The unequal weighting effects (UWEs) of the dual-frame surveys were also examined to measure increases in variance. Increases in variance due to weighting were small, and the UWE was better than in single-frame landline surveys.