The effects of temperature and milling time on the crystalline size and microstrain in WC and WC-Co powders were investigated in a cryomilling process. Within the limit of the analytical methods and TEM, the crystalline size of WC was estimated to be in the range of 50$70 nm after 10 h of cryomilling. The presence of Co in the WC-Co system significantly reduced the level of strain in the WC particles in this low-temperature processing. A thermal cycle employed in cryomilling process was also found to be useful in various aspects. Various fitting methods were compared and the results are discussed in relation to processing parameters.