In Swedish schools the interest for formative assessment practices has increased during the last decade. This can partly be seen as a response to Sweden’s poor performance in international tests and rankings but it is also reflecting the advancement of knowledge within the field. This research paper aims to examine teachers understandings of the term formative assessment and what practices they associate to the term. It is carried out by semi-structured interviews of primary school teachers. The material has then been subjected to an inductive content analysis. To ensure reliability of the results teachers have been chosen from two different municipalities and four different schools. One of the municipalities has an explicit interest in formative assessment and has developed a local program for teachers to participate in. The results of the study show a vide range of varieties in how teachers comprehend the term formative assessment. The lack of a common understanding of the term creates consequences for the equality of education, both between classrooms and between schools. Furthermore the results show that there is a correlation between the time and support teachers are given to implement formative assessment in their teachings and the depth of their understanding of the term. If the results are confirmed by further research and causality is established, further steps should be taken to examine key factors for a successful implementation.