A simulation of Cincinnati mass media system predicts frequency and reach of flow of messages from known facts taken from census statistics, newspaper and radio audience studies, and a content analysis of the press relevant to attitudes and opinions measured by NORC survey of the effects of a public information campaign on the United Nations made in 1947-48. Three trail scenarios tested plausibility of exposure and consistency with which model synthesized input data before actual scenario of 12 real themes was run. Themes most closely related to large changes shown in NORC panel were those for which simulation predicted highest average frequency of exposure. Two models relate information of attitude change to frequency of exposure and correlations are sought to themes with changes in attitudes and information and recall of exposure in NORC panel. (Author)