In-situ high-temperature scanning tunneling microscopy was used to follow the coarsening (Ostwald ripening) and decay kinetics of two-dimensional TiN islands on atomically-flat TiN(001) and TIN(111) terraces at 750-950 degreesC. The rate-limiting mechanism for island decay was found to be adatom surface-diffusion on (001) and attachment/detachment at step edges on (111) surfaces. We have modeled island decay kinetics based upon the Gibbs-Thomson and steady-state diffusion equations to obtain a 001-step edge energy per unit length of 0.23 +/- 0.05 eV/Angstrom with an activation energy of 3.4 +/- 0.3 eV for adatom formation and diffusion on TiN(001). The activation energy for adatom formation and attachment/detachment on TiN(111) is 3.5 +/- 0.3 eV.