This article investigates university students’ argumentation skills in their efforts to infl uence fellow students through language. The project was implemented at the University of Kuopio and the subjects, both Finnish and foreign university students, spoke English as a lingua franca. The students were required to argue in roles either ‘for’ or ‘against’ in videotaped debates. The aim was to determine how well they managed and what problems arose. In this demanding speech situation the students applied collaborative strategy, repetition, rephrasing and topic negotiation. Problems were caused mainly by the diffi cult topics and unknown terminology. However, there was a strong sense of commitment and joint effort.