A very simple reduction procedure is suggested for the blend viscosities of different polymer pairs. This procedure is based on the comparison of the blend viscosity, normalized either to the matrix or to the disperse phase viscosity, with the viscosities ratio of the initial polymers (eta(m)/eta(d)). We have obtained, for 13 different pairs containing 30% of the second component, the universal linear dependencies, mutual analysis of which allows connection of their special points with the stream morphology. The fibrillous morphology takes place in the range of eta(m)/eta(d) = 0, 1-5. Simultaneous, the thin skin consisting of the disperse phase polymers is formed. These results confirm the predominant role of the viscosities ratio in fibrillar composite material formation in comparison with the interphase tension phenomena.