An F11 tracer simulation is performed here using the most recent Community Climate Model, the CCM3, of the National Center for Atmospheric Research (NCAR). Another F11 simulation performed with NCAR's CCM2 <Hartley et al., 1994> is also presented. Comparing the F11 mixing ratio in the models to Atmospheric Lifetime Experiment/Global Atmospheric Gases Experiment (ALE/GAGE) F11 observations shows that the CCM3 overpredicts F11 in the northern midlatitudes, while the CCM2 has simulated F11 distributions similar to those observed. Calculating the interhemispheric exchange rate (&tgr;ex) shows that the CCM3 &tgr;ex is more than 35% slower than the CCM2. To locate why the discrepancy exists between the two models' rate of transport, tropical deep convection, the primary mechanism of interhemispheric transport, is evaluated. The CCM3 convective precipitation and convective mass flux are significantly less than in the CCM2 during the summer, coinciding with differences in the models' monthly interhemispheric transport rate. However, only the convective mass flux shows significant differences in the annual averages between the CCM2 and CCM3. It appears that the CCM3 interhemispheric transport may be slower because the CCM3 has less convective activity than the CCM2, which is most evident in the convective mass flux. The vertical velocity associated with the tropical convective area is also significantly weaker in the CCM3 during the same period when the CCM3 has less convective activity. A past study including a cumulus momentum transport parameterization with the Zhang-McFarlane convective scheme <Zhang and McFarlane, 1995b> suggests that a key issue for the CCM3 &tgr;ex may involve the parameterization's vertical resolution and lack of accounting for the momentum flux. Further research into both the subgrid scale convective mass flux and the large-scale circulation effects of the convective parameterization would be helpful in determining what is needed to improve the CCM3 interhemispheric transport rate. ¿ 1998 American Geophysical Union