The shape of the meniscus separating 2 immiscible fluid phases in a rotating, vertical, cylindrical tube was calculated numerically from Laplace's equation of capillarity, for the case of complete wetting of the tube wall by the lower fluid.Values of the exptl. most accessible quantity, the vertical displacement of the bottom of the meniscus, are given in detail as a function of speed of rotation and capillary constantExptl. displacements agree with theor. predictions.The numerical data can be used to determine surface and interfacial tension.The method has certain exptl. advantages over the method of spinning drops in a horizontal tube.However, an error anal. indicates, and the experiments confirm, that the method becomes clearly inferior for low interfacial tensions, because of the increasingly dominant influence of gravity under these conditions.The influence of incomplete wetting was considered.