This research is a study on the Students Problems in Transactional Speaking on English Foreign Learners (EFL) FKIP Nommensen Pematangsiantar. In this research, the problem is “What are the students' problems in vocabulary when they are speaking English?”To answer the problem of the study the writer follow some theories namely Nunan (1991) which concern with definition of speaking and the elements of speaking, Brown (2001) which concern with types of speaking performance, Richards (2008) which concern the functions of speaking, Ur (1996) which concern with some difficulties in speaking, Thornburry (2005) which concern with classroom speaking activities and Keegen (2009) which concern with descriptive qualitative research. The methodology which is used in this study is qualitative research, which purposes to find out the result of this research. This subject of the study is the students transactional speaking the second semester academic year 2017. The object of the study is the students' problems in vocabulary when they are speaking English. To collect the data, the writer use test as instrument by asks the students to practice promoting product. The data analysis shows that most of the students face problems in vocabulary namely the choice of word inaccurate, the arrangement of word is wrong and limitations of vocabulary. Finally the writer concludes that the students have problems in speaking English. The students face some problems in vocabulary namely the choice of word inaccurate, the arrangement of word is wrong and limitations of vocabulary. The writer hopes that this research can be useful for the readers.