This thesis analyzes the current state of the language immersion program in Catalonia after its implementation 30 years ago, and after the immigration wave of the last decade. The language immersion is a method of teaching a second language using a language of instruction different than the students’ mother tongue. The Catalan authorities use this as a method for preserving Catalan in the society.The aim of this study is to examine the use of Catalan at school and outside of school by students who have followed the language immersion program. Language attitudes play an important role for the maintenance of a minority language, as Catalan. Therefore, in this study, the informants’ attitudes towards Catalan have also been measured. The method applied is a quantitative method where the informants have answered a written questionnaire. The results show a high level of knowledge of Catalan and its frequent use in the classroom. In contrast, outside of school the Castilian language is more often used. The informants seem to have a positive attitude towards Catalan.The conclusion is that the language immersion works satisfactory in a school context but often fails outside of school.