Theory lectures are boring and sleep inducing for students, and it is difficult to get their full attention during 1 h of lecture. The ability of students to concentrate diminishes 20-25 min after the start of the lecture. There is also a lack of active participation of students during theory lectures. In an effort to break the monotony of the lecture, an online blood grouping game was used to engage the students during a lecture on blood groups. After a 30-min lecture on blood grouping, 100 first-year medical students were given the opportunity to play the game in the lecture hall computer. These students are equivalent to the United States undergraduate college students. The activity consisted of blood grouping followed by transfusion of the appropriate blood to a virtual patient. A few students volunteered to play the game. The remaining students watched the game projected in the lecture hall. The spectators also helped the volunteers in doing the blood grouping and transfusion correctly. Feedback on the activity was taken at the end of the session using a questionnaire.