This study aims to determine the views of the teacher and students views on a practice carried out by using group investigation technique of cooperative learning method. The study was conducted with 20 students at 8th grade at a public elementary school in Trabzon during the spring term of 2008-2009 school year. Case study research method was used in this study. Data were collected via informal interviews and observation forms. The data gathered from the interviews were analyzed and presented in tables and networks whereas observation data were given in tables. In the light of the data collected from this study; during the group study, the students enjoyed working in groups, found the group investigation technique useful, undertook several roles and moved from an individual to a cooperative stance in the group. Based on these results, group investigation technique is recommended to be used in secondary and higher education mathematics courses.Key Words: Coperative learning, group investigation, teacher and student views