Molybdenum powder was ball milled for times ranging from 90min to 180h in a steel vessel with hardened steel balls under Ar atmosphere. The milling products were examined by X-ray diffraction. The methods of Williamson and Hall, Warren and Averbach and an alternative method after van Berkum et al. for the separation of size and strain contributions were applied to the profiles. Differences and similarities between the results of the various methods were discussed.