The time evolution integrodifferential equation for the ensemble mean of an advected passive scalar is derived for a general ensemble of compressible flows. Eulerian one‐point,n‐time velocity correlation functions and their spatial derivatives are required in the equation. The equation is applied to a case for which an exact solution is already known, and the validity of certain formal operator manipulations is demonstrated. A simple closure is discussed and the results are compared with other established results. Suggestions for further studies are made.