Application of robust design techniques in the design of controllers for Autonomous Underwater Vehicles (AUVs) is discussed in this paper. Proper tuning of controllers is essential in achieving the desired positional and tracking accuracy of AUVs in underwater missions. A new scheme of gain tuning using Taguchi method is introduced here for the proportional-integral-derivative (PID) control of an under-actuated AUV with less controllable degrees of freedom than the total number of degrees of freedom. With four controllable states, this vehicle has twelve controller gains to be tuned. Through the help of design of experiments (DOE) and robust design techniques, as applied in the Taguchi optimization method, an optimal and robust set of PID controller gains have been obtained. A simulation study of the pitch control of an AUV using the above method is presented in the paper. The simulation results are compared with the other tuning methods like Ziegler - Nichols, Auto tune, Tyreus - Luyben and Cohen-Coon method. The results show that the index of aggregate absolute error has reduced to 78.73% and 24.34% from the Ziegler - Nichols method 1 and Tyreus-Luyben method respectively. Copyright © 2009 by The International Society of Offshore and Polar Engineers (ISOPE).