This document specifies methods by which the measurement of power (energy) density distribution is made and defines parameters for the characterization of the spatial properties of laser power (energy) density distribution functions at a given plane. The methods given in this document are intended to be used for the testing and characterization of both continuous wave (cw) and pulsed laser beams used in optics and optical instruments. This document provides definitions of terms and symbols to be used in referring to power density distribution@ as well as requirements for its measurement. For pulsed lasers@ the distribution of timeintegrated power density (i.e. energy density) is the quantity most often measured.