We establish upper and lower bounds for the entries of the inverses of diag
onally dominant tridiagonal matrices. These bounds improve the bounds recen
tly given by Shivakumar and Ji. Moreover, we show how to improve our bounds
iteratively. For an nxn M-matrix this iterative refinement yields the exac
t inverse after n - 1 steps. (C) 1999 Elsevier Science Inc. All rights rese
rved.