  We discuss the thermal evaporation of tiny HI clouds in the interstellar
medium. Cold neutral clouds will take ~10^6 - 10^7 yr to evaporate if they are
embedded in warm neutral gas and about half as long if embedded in hot gas.
Heat flux saturation effects severely reduce the evaporation rate of tiny cold
neutral medium (CNM) clouds into hot gas. For CNM clouds embedded in warm
neutral medium (WNM) the much lower conductivity results in slower evaporation.
This mass loss rate could still be significant, however, if the environment is
relatively quiescent. Partial ionization of the WNM gas would substantially
reduce the conductivity and lengthen the lifetime of the tiny HI clouds. The
ultimate importance of thermal conduction to cloud evolution will depend on the
role of turbulence and the characteristics of the medium in which the clouds
are embedded.
