The paper presents a case study of an ESP course illustrating the implementation of formative assessment to increase students' participation and motivation. Formative assessment is an ongoing process teachers and students engage in while focusing on the learning goals and taking action to achieve them. It refers to monitoring students' learning and the in-process evaluation of student performance by the teacher and by peers providing ongoing feedback to both the teacher and the students. The "Business English for Engineers" course, designed for graduate students of mechanical engineering, focuses on developing the presentation skills of future mechanical engineers. The students enrolled on the course prepare presentations on engineering topics planned by the syllabus, thus taking direct responsibility for learning. The presentations are followed by questions and group discussions on the presented topics and are subsequently assessed by the rest of the students, the presenters themselves and the teacher. Apart from presentations, students are also assigned smaller tasks to do in class in pairs or groups. A grade in the form of points is attached to the delivered presentations and completed tasks, contributing to the student's final grade. The results of the questionnaire completed by the students at the end of the course show that such formative activities and assessment increased the students' motivation and participation in class.