The Boltzmann entropy of a superthermal distribution modeled by a kappa function is calculated. It is shown that, for adiabatic transport, the quantity (T3/2core/n)&xgr;(&kgr;) remains constant where Tcore is the core Maxwellian temperature, n is the density, and &xgr;(&kgr;) is a function of the high energy spectral index, &kgr;. For large values of kappa commonly found in space plasmas (&kgr;>4), the quantity T3/2/n where T={&kgr;/(&kgr;-3/2)}Tcore is approximately constant for adiabatic transport. ¿ American Geophysical Union 1995.