A communication model based upon exposure, information transmission and attitude change is proposed. Particularly the information transmission is dealt with in connection with a campaign for the Danish Railroads. This campaign has as its main purpose to inform about the introduction of the Intercity trains in Denmark. To control the extent to which this purpose was met a test program was designed covering a sequence of pre and post campaign measures. In both pre- and post-tests, attention, attitude and knowledge was measured. The latter which was of major importance for the campaign was measured with the use of true/false statements covering items being critical for the campaign. Results of the pre-test suggest that the campaign is communicating extremely efficiently. When exposure is obtained, the post-test shows that the campaign actually did get across the information to an extent which was predicted by the pretest. In conclusion it is discussed how the combined use of pre and the post-test procedures provides a way of increasing our understanding of the communication process, and how the definition of campaign content and communication purpose is vital to the testing procedure.