Most viscous liquids used in chemical and food industries are highly viscous and non-Newtonian. One of the best impeders for the agitation of these Liquids i a helical ribbon impeller. In this investigation, power consumption measurements for helical ribbon impellers of various number of ribbons were carried out in the range of laminar flow. Glycerol molasses and CMC water solutions were used as mixed liquids. The experiments were made using nat-bottomed mixer with D=0.15 m (Fig. 1) equipped with helical ribbon agitator (Fig. 2). The effect of ribbon number on the power consumption is shown in Fig. 3 and generalized by Eq. (6). Numerous reports have been published concerning experimental studies in this field, but these researches were performed for ribbon agitators with n(b)=1 or n(b)=2. The present experimental studies were made for agitators with n(b)=1-4. It has been shown that the number of ribbons monotonically influences the power consumption. As follows from Fig. 4, the values of product Ne Re increase as the number of ribbons increases. The Reynolds number for non-Newtonian liquids was calculated using the method of Metzner and Otto [1]. In this method, the effective shear rate is evaluated from Eq. (3). The B-values depend on geometrical parameters of agitators. From the study of earlier papers in this field it appears that the effect of ribbon number on mixer shear rate constant has not been investigated so far. This effect has been investigated in the present paper and correlated in Eq. (9). The maximum value of effective shear rate was reached for n,=3.