Not participating in speaking activities is a common problems in the English as a Foreign Language bachelor classes of the second degree of Cantho University, Vietnam, but according to Ur (1996) speaking seems to be the most important skills of all the four skills. Many of the students are middle-aged ones that are used to Grammar translation method in their past study. To solve this problem, I used ‘role- plays’ to create many situations for them to speak out. Twenty four students of the 16th Language Kiengiang course trained by Cantho University were selected. They were in the first semester of the first year with the subject, Communication 1, and almost all of them were at pre-intermediate level of listening and speaking skill. Most of them were in their 30s and 40s, and five of them were in their 20s and three in their 50s. Ten sessions were treated with ten types of activities of role-plays done in pairs, small groups, big groups and the whole class. With daily observation, interviews, a questionnaire the result was that ten role-plays helped the working adult students in their 20s-50s to participate in speaking English significantly. Although it was difficult for the 50s, they could fulfil their talk in a basic and short answers with the help of the teacher. The role-plays in pairs and small groups helped the weak students than the big group but the tasks of big group were more effective for good students. Therefore, I suggest that role-plays should be used in the working adult students.