This paper presents a sensorless control for a stall regulated variable speed wind turbine, where the speed reference is obtained from the estimated aerodynamic torque. The LQG/LTR methodology is applied to the design of an optimal discrete-time feedback controller for a Wind Energy Conversion System, aiming to maximize the efficiency on energy conversion and to minimize the detrimental dynamic loads due to wind fluctuation and ripple torque. The trade-off between the efficiency maximization of the energy conversion and the dynamic load effects minimization is considered in the quadratic cost function of the LQG/LTR design. The resulting control structure is simulated considering a step variation on wind speed. The performance of the proposed control scheme is discussed showing that it really leads the WECS operation near to the maximum efficiency point and reduces the detrimental dynamic loads. It is also presented some alternatives for sensorless control for the electrical generator.