Abstract: The present invention provides a method of analysing a sample comprising sub-micron particles, comprising determining first information about the size of particles and number of particles in the sample by nanoparticle tracking analysis; determining second information about average particle size of particles in the sample by dynamic light scattering; determining from the first information third information representing the theoretical effect of the detected particles on results obtainable by dynamic light scattering; and adjusting the second information using the third information to produce fourth information representing adjusted information on average particle size.