We created and evaluated an 8-month campaign of provocative radio ads to change attitudes about concurrent (overlapping) sexual partnerships among young African Americans. We created a concurrency attitude scale and compared its score distributions in independent samples of African Americans, ages 18-34 years, interviewed by telephone before (n = 678) and after (n = 479) the campaign. Pre- and post-campaign samples reflected similar response rates (pre: 32.6%; post: 31.8%) and distributions of personal characteristics. Reported exposure to concurrency messages was greater after the campaign (pre: 6.3%, post: 30.9%), and mean scores indicated less acceptance of concurrency (pre: 3.40 [95% CI 3.23, 3.57]; post: 2.62 [2.46, 2.78]). Score differences were not a function of differences in composition of the samples (adjusted means: pre: 3.37 [3.21, 3.53]; post: 2.62 [2.47, 2.76]). Findings demonstrate that a carefully targeted, intensive mass media campaign can change attitudes about concurrency, which should facilitate behavior change.