Non-lethal weapons (NLWs) are designed to minimize fatalities and other undesired collateral damage when used. Events of the last few years including the attack on the USS Cole have raised ideas about the role NLWs can play in enhancing support to naval forces. In particular to what extent and in what areas should Department of the Navy (DoN) -sponsored science and technology (S&T) provide a research base for developing NLW capabilities? To assist with this question and to evaluate the current NLWs program, the Joint Non-Lethal Weapons Directorate (JNLWD) and the Office of Naval Research (ONR) requested the National Research Council perform an assessment of NLWs science and technology. The report presents the results of that assessment. It discusses promising NLW S&T areas, development accomplishments and concerns about NLW, and series of recommendations about future NLW development and application.