A computational methodology is proposed to predict the running clearance of a six-tooth straight-through rotating labyrinth seal numerically by taking into account both the centrifugal and thermal growths. Four different angular velocities ranging from 0 to 3000 rad/s are chosen to study the influence of rotation on the leakage flow rate. The detailed leakage flow fields and the structural deformations are presented. Further, different pressure ratios in the range of 1.1 to 2.5 have been investigated for a wide range of initial clearances. The methodology is validated against the available data in the literature. It is found out that there is a significant reduction in leakage flow rate by incorporating the radial growth for a particular operating condition. However, for a given initial clearance, the rotation has negligible effect on the reduction in the leakage flow rate, except at pressure ratios lower than 1.7. Further; the rotation has more prominent effect for smaller clearance values. Copyright © 2013 by ASME.