Mass media can spread information and disinformation, but its impact is hard to rigorously measure. Using a two-level randomized evaluation covering 5 million people, we test both exposure to mass media (with 1,500 women receiving radios) and the impact of a high-quality, intensive 2.5 year, family planning mass media campaign in Burkina Faso (8 of 16 local radio stations received the campaign). We find women who received a radio in noncampaign areas reduced contraception use by 5.2 percentage points (p=0.039) and had more conservative gender attitudes. In contrast, modern contraceptive use rose 5.9 percentage points (p=0.046) in campaign areas and 5.8 percentage points (p=0.030) among those given radios in campaign areas. Births fell 10%. The campaign changed beliefs about contraception but not preferences, and encouraged existing users to use more consistently. We estimate the nationwide campaign scale-up led to 225,000 additional women using modern contraception, at a cost of US$7.7 per additional user.