Optimal control is a key element in today’s control applications, being widely used in many different fields. The linear-quadratic regulator (LQR) is an optimal control method which is frequently used in optimal control applications because of its efficiency and simplicity. Having this in mind, the authors studied the level control of a cascaded multitank system using the LQR algorithm. The approach of the authors consists of a piecewise linearization method, converting this nonlinear problem into a linear one. Results show that LQR is a very efficient method for this type of system, yielding good performances with reduced controller effort.