The influence of fructooligosaccharide (FOS) and whey protein concentrate (WPC) on the rheological characteristics was studied in reduced-fat probiotic yoghurts containing 1.5% milk fat and 1.5% FOS or 1.5% WPC during a storage period of 28 days. These properties were examined in comparison to control yoghurts containing 1.5% and 3% milk fat and no supplement. Sensory characteristics of the products were also evaluated. Addition of WPC to reduced-fat probiotic yoghurt significantly decreased the syneresis and increased the water holding capacity on the 14(th) and 28(th) days of storage (p<0.05). Viscosity was also promoted; however, the firmness index decreased with the use of WPC (p<0.05). Furthermore, a significant decline was obtained in the viscosity of the samples containing WPC at the end of storage (p<0.05). With regard to sensory characteristics; flavour, appearance and texture did not vary depending on the presence of FOS or WPC, while supplementation of FOS developed the taste of the products (p<0.05).