A new formulation of an approximate conservation relation is proposed for stationary Rossby waves on a zonally varying basic flow utilizing that A (proportional to wave enstrophy) and E (proportional to wave energy) are both related to the wave activity pseudomomentum. For stationary Rossby waves, it is shown in the limit of a small-amplitude plane wave on a slowly varying, unforced non-zonal flow that a particular linear combination of A and E namely. M≡(A+)/2, is independent of the wave phase, even if unaveraged, and is conserved under steady, unforced and nondissipative conditions. It is also shown that the three-dimensional flux of M is parallel to the local group velocity in the WKB limit. The flux could be a useful diagnostic tool, as shown in an example that presents a snapshot of the three-dimensional propagation of a stationary Rossby wavetrain in the real atmosphere. Our conservation relation is a generalization of that for stationary Rossby waves on a zonally-uniform basic flow derived by Plumb. ¿ 1997 American Geophysical Union