Research concerning the success factors in language immersion education is reviewed, focusing on five major schools of thought. First, the traditional model for immersion research, implemented in a Montreal (Canada) suburb is examined. Then three studies of the influence of affective variables in immersion program success are examined, and it is noted that no theoretical overview of the importance of the affective aspects is known. Theorists and researchers considering the social facet of the immersion process and two works on the interrelationship between social and affective factors in the immersion setting are discussed next. Finally, Stephen Krashen's monitor model is compared with the others, and found to be the most relevant to immersion theory. A 27-item bibliography is included. (MSE)