Abstrak
This research discusses interference. The writer discussed first language interference in speaking English to students of grade A of SMP N 7 Sabu Barat. It is one of bilingualism aspects that occur when someone is learning his/her English. In this case, the interference of mother Tongue into English. It is chosen because students sometimes use their mother tongue that often contains error when they are speaking English. The purpose of the study is to find out types of interference and factors cause interference. The writer focused on speaking English of reading story in the classroom. The writer used descriptive qualitative method. Data were collected from observation and audio recording. The writer selected some sentences included interference by using Weinreich theory and analysed them. As a result of the research, the writer found that most of the students do interference in words pronunciation that they didn’t know how to mention correct vocabulary in English, then in grammatical patterns from which students tend to use their mother tongue grammatical patterns and the vocabulary used they applied their mother tongue when the students do not get appropriate word to express their mind