Precipitation of BaSO4 has been studied in a vessel of similar to8 l stirred by a Rushton turbine. Either BaCl2 or Na2SO4 as a limiting reactant of concentration 0.1 M was added to the tank containing the opposite component at a concentration from 0.0018 to 0.027 M, thereby giving total molar ratios from 1/15 to 1 or 1 to 15/1, respectively. The results were generally not symmetrical. Molar ratios closest to 1 with BaCl2 as the feed gave the largest d(43) (similar to 20-30 mum) whilst for Na2SO4 feed, the mean size d(43) was similar to 10-15 mum. At the ratios 1/15 (BaCl2 feed) and 15/1 (Na2SO4 feed), the mean sizes were much smaller and very similar (similar to3-5 mum). In all cases, the CoV was similar to0.4 - similar to0.5. The impact of agitation speed was generally rather small. It is suggested that varying ionic ratios might be an effective and rather simple way of achieving a degree of particle size control.