A study was conducted in a B-737 full flight simulator at the Boeing Customer Training facility to evaluate pilot decision making and performance under various situations in which decisions on whether or not to reject a take off had to be made and executed. A total of eight (8) situations were defined in which Go/NoGo decisions had to be made near V1 speed. Subjects included 24 Boeing instructor pilots and 24 line pilots from five different airlines. The sequence in which pilots encountered the situations was carefully balanced across subjects to control for learning effects. The results of the study are reported as quantitative data on RTO decisions, stopping performance, and procedure accomplishment plus a summary of data derived from post-run debriefings of the airline pilots. Lessons learned, conclusions, and recommendations for RTO training are presented.