Structural waves in a cylindrical shell can be decomposed into different circumferential modes. The energies carried by these modes usually need to be quantified and ranked for the purposes of noise and vibration control. In this paper, a theoretical basis is outlined for a method to measure the energy flow components of different circumferential modes through a cross-section of a circular cylindrical shell. This new method has potential to measure energy flow carried by higher order circumferential modes (n greater than or equal to 3). Experimental results obtained on a thin-walled circular cylindrical shell show that this proposed method can be used to accurately measure the total energy flow and its components. (C) 2001 Academic Press.