“Proportionality” has become a common term, widely used by human rights organizations, politicians, soldiers and laypersons, but its precise legal meaning is little understood. The goal of this paper is to clarify the parameters of the use of the term and identify the problems confronting attempts to apply it. The final section of the paper mentions various solutions to these problems and alludes to the concept’s application in the context of the present war between Israel and Hizballah.