This work shows the application of several experimental methods to the measurement of the interfacial tension, sigma, between two immiscible polymers. a quantitative knowledge of the interfacial tension is important in view of the crucial role that this parameter plays in polymer blend processing. Common to all methods presented here are two main points. The first is that a is obtained from experiments where the shape of the interface between the liquids is directly observed by means of optical microscopy techniques. The second point is that the interface geometry is controlled by a balance between the interfacial force and the viscous stresses generated by some flow applied to the system. Measurements have been carried out on a model polymer blend, whose constituents are a poly-isobutylene and a polydimethylsiloxane, both transparent and Liquid at room temperature. When compared with each other, the values of interfacial tension obtained from the different methods show a good quantitative agreement. Excellent agreement is also found with results for the same system previously published in the literature.