We examine the effect of online Argumentation Vee Diagrams (AVDs) on the quality of students' argumentation during asynchronous, online discussions. With AVDs, students develop arguments on both sides of a controversial issue and then develop an integrated, overall final conclusion. In this study, students used AVDs individually before composing discussion notes, and then--at the end of the discussion--jointly created a group AVD using "Wiki" technology. Compared to a control group, the experimental intervention was found to significantly enhance the integration of arguments and counterarguments (specifically, compromises) and fostered opinion change. For AVDs to be effective, however, it was found to be necessary to include specific scaffolds on how to evaluate argument strength and/or to provide practice and feedback in using the AVDs.