Sliding mode design based on Lyapunov matrices is proposed as roll autopilot for a tail controlled missile. The search of Lyapunov matrix for systems with unmatched uncertainties is formulated in terms of linear matrix inequality. The proposed scheme ensures robust roll position control even in the presence of large mismatched parametric uncertainties and external disturbances. The performance of roll autopilot design based on sliding mode technique is compared with the classical autopilot. The simulation results demonstrate that the sliding mode based roll autopilot maintains its performance over wide range of variation of parameters. © 2010 IEEE.