Luminescence effect of particle surface stressed during milling operation was used to correlate the size of the ZnS/Cu particles. Both the amount of structural defects in solids and the area of newly created surface increase with the grinding intensity and time. The intensity ratio at two different wavelengths (400 and 500 nm) is found to be suitable for measurements of the particle size. This kind of measurement of particle size is insensitive to the particles aggregation and presence of abrasive substance in the suspension. (C) 2004 Elsevier B.V. All rights reserved.