Kyunghee Yeo. 2000. A Case Study on the Subject-Exchange Teaching Systems in Elementary English Class: a Transitional Scheme of Problem-Solving. Studies in Modern Grammar 20, 199-213. It goes without saying that a teacher who is responsible for the effective teaching is one of the most important factors in teaching-learning situation. The controversy over who should teach English to elementary school students has continued since English was introduced in elementary schools in 1997. There are two systems in which English can be taught in elementary schools. One is the system in which a classroom teacher who has the deepest understanding toward his/her students teach English. The other is the system in which a subject teacher who has good command of English teach English. Generally, the Ministry of Education encourages the classroom teacher to teach English to children and the teachers who have little confidence in teaching English prefer the system in which a subject teacher teaches. Both systems are said to he strengths and weaknesses. This paper suggests the subject-exchange teaching system that compromises above mentioned two systems and shows how elementary school teachers think of this system and illustrates the case and the effects of subject-exchange teaching system.