['Teamwork during cardiopulmonary arrest events is important for resuscitation. Teamwork improvement programs are usually lengthy. This study assessed the effectiveness of a 2-hour teamwork training program.', 'A prospective, pretest/posttest, quasi-experimental design assessed the teamwork training program targeted to resident physicians, nurses, and respiratory therapists.', 'Participants took part in a simulated cardiac arrest. After the simulation, participants and trained observers assessed perceptions of teamwork using the Team Emergency Assessment Measure (TEAM) tool (ratings of 0 [low] to 4 [high]). A debriefing and 45 minutes of teamwork education followed. Participants then took part in a second simulated cardiac arrest scenario. Afterward, participants and observers assessed teamwork.', "Seventy-three team members participated-resident physicians (25%), registered nurses (32%), and respiratory therapists (41%). The physicians had significantly less experience on code teams (P < .001). Baseline teamwork scores were 2.57 to 2.72. Participants' mean (SD) scores on the TEAM tool for the first and second simulations were 3.2 (0.5) and 3.7 (0.4), respectively (P < .001). Observers' mean (SD) TEAM scores for the first and second simulations were 3.0 (0.5) and 3.7 (0.3), respectively (P < .001). Program evaluations by participants were positive."] Does two Hours of Teamwork Training improve Teamwork in Simulated Cardiopulmonary Arrest Events?