Results are presented for experiments which examine the ability of the University of Wisconsin (UW) hybrid isentropic-sigma (&thgr;-&sgr;) and sigma (&sgr;) coordinate models and the NCAR Community Climate Model 2 (CCM2) to transport and conserve the joint distributions of potential temperature (&thgr;) or equivalent potential temperature (&thgr;e) and a source-free inert trace constituent identical to the respective initial distribution (t&thgr; or t&thgr;e). Under the idealized isentropic conditions of these experiments, the governing equations for the atmospheric continuum require that the joint distributions (&thgr;, t&thgr; or &thgr;e, t&thgr;e) be conserved throughout the integration. Deviation in the paired values is an objective measure of a model's skill to conserve the joint distributions. Results show that conservation remains higher in the UW &thgr;-&sgr; model than in the other models, even near the interface between isentropic and sigma model domains.¿ 1997 American Geophysical Union