A three-phase longitudinal study (spread over a month's time) was carried out to investigate attitude's persistence and linkage to behavior as it may be affected by the processing of information about the communication source. The following three independent variables were manipulated: (i) contents of the source of information (implying the communicator to be expert or inexpert on the topic of the communication); (ii) length of the source information (brief versus lengthy); and (iii) message recipients' involvement in the issue at hand (high versus low). Replicating prior research when the source information was brief, it exerted greater persuasive impact under low versus high involvement, and when it was lengthy, it exerted greater persuasive impact under high versus low involvement. Of greater importance, the newly acquired attitudes were more persistent and were linked more strongly to actual behavior when the source information was lengthy (versus brief) provided the recipients had high (versus low) involvement in the issue. These findings were interpreted to mean that just like with the message/issue information in prior research, when processed extensively, source information, too, may contribute to the formation of persistent and behavior-driving attitudes. Copyright © 2011 John Wiley & Sons, Ltd.