The synthesis examines what effects Content and Language Integrated Learning has on oral production in English. Relevant frameworks such as the 4Cs Framework and the Language Triptych as well as language learning theories such as the Sociocultural Theory and Krashen's Second Language Acquisition Theory have been examined and an in-depth presentation is given. The current findings on Content and Language Integrated Learning in Sweden are presented and a discussion on how English is portrayed in the Swedish National Curriculum is further concluded. Later the results of six recent studies about the effects that Content and Language Integrated Leering has on primary school students as well as comparisons between Content and Language Integrated students and mainstream English education students are presented. The presented outcomes of the studies are discussed and linked to the theories, the 4Cs Framework, and the Language Triptych. Finally, a conclusion is made based upon the findings answering the research questions on What impact could Content and Language Integrated Learning applied in Swedish primary schools have on oral proficiency in English? And why does/does not Content and Language Integrated Learning affect English oral language development in Swedish primary schools?