This paper investigates the grindability of calcite powder (D-50 = 6.68 mu m) to submicron particle sizes using stirred media mill (0.75 l) and ultrasonic generator (400 W, 24 kHz). The present study focuses directly on the comminution of calcite powder in water media by combined stirred milling and ultrasonic treatment and effects of some operational parameters such as grinding time (10-30 min), ultrasonic power (40-100% mu m as amplitude settings), and solid ratio (10-30% w/w) on comminution. Experimental results have been evaluated on the basis of product size and width of particle size distribution.