  We compare the probabilities of arm events in two-dimensional invasion
percolation to those in critical percolation. Arm events are defined by the
existence of a prescribed color sequence of invaded and non-invaded connections
from the origin to distance n. We find that, for sequences of a particular
form, arm probabilities in invasion percolation and critical percolation are
comparable, uniformly in n, while they differ by a power of n for all others. A
corollary of our results is the existence, on the triangular lattice, of arm
exponents for invasion percolation, for any color sequence with at least two
open (invaded) entries.
