The fundamental problem in control engineering is to providerobust performance to uncertain plants. H -control theorybegan in the early eighties as an attempt to lay downrigorous foundations on the classical robust controlrequirements. It now turns out that H -control theory is atthe crossroads of several important directions of researchspace or polynomial approach to control and classicalinterpolation theory; harmonic analysis and operator theory;minimax LQ stochastic control and integral equations. Thebook presents the underlying fundamental ideas, problems andadvances through the pen of leading contributors to thefield, for graduate students and researchers in bothengineering and mathematics. From the Contents: C. Foias: Commutant Lifting Techniquesfor Computing Optimal H Controllers.- B.A. Francis:Lectures on H Control and Sampled-Data Systems.- J.W. Helton: Two Topics in Systems Engineering Frequency Domain Design and Nonlinear System.- H. Kwakernaak: The Polynomial Approach to H -Optimal Regulation.- J.B. Pearson: A Short Course in l – Optimal Control