Although there are earlier experiences from computer mediated communication (CMC) applications in which e-mail has been used as a forum for argumentation and debate, the literature lacks systematic analyses on the use of CMC for this purpose. This kind of analysis would produce knowledge on the relevance of CMC for practicing argumentation that is needed in developing study methods which could meet especially the goals of higher education. The research tasks of this study were: (1) to examine the level and development of argumentation and counterargumentation in the students' e-mail messages; and (2) to clarify associations between the quality and quantity of argumentation and counterargumentation and two different e-mail study modes. Subjects were 31 students in the Department of Education at the University of Jyvaskyla, Finland. Two top students in the field of education near their graduation were also recruited as tutors of the e-mail studies. Results indicated that the level of argumentation in the students' messages improved during the e-mail study period and that the level of argumentation was higher in the counterargumentative messages compared to those in which the writer had not attacked other peoples' standpoints. In addition, it was found that the average level of argumentation in the students' messages was considered to be quite low. The small portion of argumentative messages indicated also that disputes and debates between the students were uncommon. These results point to the need to develop study methods based on critical discussions and learning environments in the Finnish system which encourage debates, critical interaction, and exchange of opinions. (Contains 46 references.) (AEF)