This paper deals with the design of stable adaptive controllers using a model reference approach. A systematic procedure is developed using the concept of positive realness and is generalized to arbitrarily located coutrol parameters. For plants withnpoles and(geq)(n-2)zeros, the uniform asymptotic stability in the large of the adaptive loop is demonstrated. For plants with(leq)(n-3)zeros the stability problem is clawed and is stated as a conjecture. Simulation studies of the adaptive control of both stable and unstable plants are included towards the end of the paper.