The phenomenon of mass inflation is shown to occur for a (2+1)-dimensi
onal rotating black hole. We demonstrate this feature by extending the
spinning BTZ black hole to Vaidya form. We find that the mass functio
n diverges in a manner quantitatively similar to its static counterpar
ts in 3 + 1, 2 + 1, and 1 + 1 dimensions, but unique features of Einst
ein theory in 2+1 dimensions contrast the physics in the BTZ black hol
e with that in 3 + 1 and 1 + 1 dimensions.