Observations of linearly increasing (e.g., SF6) and periodically varying (e.g., H2O+2CH4) long-lived tracers in the lower stratosphere provide independent constraints on theories of transport in the region. Taken together, these data allow separation of the roles of diffusion (with coefficient K&thgr;) and advection (at rate Q) through isentropic surfaces, and mixing of extra-tropical air into the tropics (with relaxation time &tgr;). Using a one-dimensional diffusive-advective model of the tropical stratosphere, which allows relaxation of mixing ratios to extra-tropical values, we obtain solutions for periodic and linear tracers. Fitting the solutions to observations yields K&thgr;≈0.3 K2/day (Kz≈0.01 m2/s), &tgr;≈1.3 years, and Q≈0.5 K/day (w¿≈0.3 mm/s). These values produce profiles for CO2 in reasonable agreement with aircraft observations. However, a large range of K&thgr; results in equally good agreement, although &tgr; and Q are more tightly constrained. In the lower tropical stratosphere, vertical diffusion appears to play little role in transporting tracer.¿ 1997 American Geophysical Union