A singular perturbation analysis of the partial cheap control of the linear time-invariant regulator is presented, in which some but not necessarily all of the control inputs have arbitrarily small cost weighting. In the limit, them2initial cheap control inputs arc impulsive, while the outer solution asymptotically approaches a singular are associated with a dynamical system and matrix Riccati equation, both of ordern–m2. A two-time-scale decomposition of the regulator problem yields a slow control and a composite control that provide near-optimal performance. Further, the partial cheap control results are used to solve the dual almost singular optimal linear filtering problem.