ISO 22412:2008 specifies a method for the application of dynamic light scattering (DLS) to the estimation of an average particle size and the measurement of the broadness of the size distribution of mainly submicrometre-sized particles or droplets dispersed in liquids. ISO 22412:2008 is applicable to the measurement of a broad range of dilute and concentrated suspensions. The principle of DLS is the same as for a dilute dispersion. However, specific requirements for the instrument set-up and specification of test sample preparation, as well as some advice on the correct interpretation of the results of measurements for concentrated dispersions, are required.