The primary objective of this study is to examine tho sensitivity properties of a multilinear plant embedded in a feedback structure. As a prelude tho existing linear theory ia summarized and extended. Tho bilinear case is then treatod in detail. Extrapolation to the multilinear ease has been carried out by Porter and DeSantis (1974 a). New results includo the following : (i) the use of causality structure as a component of sensitivity analysis in closed-loop linear and non-linear systems, (ii) the establishment of terminal equivalence conditions for multilinear plants and multilinear compensators, (iii) the development of a sensitivity operator in the multilinear setting including existence conditions, (iv) extensions of linear results to largo parameter perturbations.