Chocolates with reduced calories have become popular among consumers and manufacturers. One way of manufacturing chocolate with reduced calories is to replace sucrose with some alternatives. Effects of different bulk sweeteners (maltitol, isomalt, and xylitol) with different particle size intervals (PSI) (106-53, 53-38 and 38-20 mu m) on rheological properties of molten chocolate were investigated. The best model that fit the rheological data was Herschel-Bulkley model. Maltitol resulted in similar rheological properties of chocolate compared to sucrose and thus can be a good alternative. Isomalt resulted in higher plastic viscosity while maltitol resulted in higher yield stress than others. As the particle size increased the plastic viscosity and the yield stress increased. The differences in rheological properties of chocolate with different bulk sweeteners were caused by differences in solid volume fraction and particle size distribution (PSD). A substitute with large particle size should be chosen to replace sucrose for improving rheological properties of chocolate, but the particle size should be small enough to obtain good sensory properties. (c) 2006 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.