The weakly conditionally stable (WCS) finite-difference time-domain (WCS-FDTD) method in the cylindrical coordinate system is employed to compute the electromagnetic coupling and shielding of various cylindrical enclosures. In the WCS-FDTD method, a larger time-step size than that allowed by the Courant–Friedrich–Levy stability condition limitation can be set because the algorithm of this method is WCS. Consequently, an increase in computational efforts caused by fine cells due to thin sots can be prevented. The results from the WCS-FDTD method agree well with the results from the conventional FDTD method, and the required CPU time for the WCS-FDTD method is much shorter than that for the FDTD method. Careful investigation of different aspects of the shielding properties of the cylindrical enclosures is performed, and the shielding performance of the cylindrical enclosure and rectangular enclosure is compared. The result obtained in this paper can be used to design a practical cylindrical shielding enclosure. Copyright © 2010 John Wiley & Sons, Ltd.