Current training device evaluations performed in-plant do not adequately address instructional subsystem issues. Instead, these tests focus primarily on engineering topics. Formative evaluation is a method which allows training device designers and users to determine instructional subsystem problems before the device is shipped. It also provides opportunities to make improvements. This paper defines training device formative evaluation, describes its purposes and techniques, and points out possible obstacles to its conduct. The paper concludes with an example of formative evaluation which was performed on the M1 Tank Institutional Conduct of Fire Trainer.