  We study the decays Omega^- -> Cascade+pion using heavy-baryon chiral
perturbation theory to quantify the |Delta I|=1/2 rule in these decay modes.
The ratio of |Delta I|=3/2 to |Delta I|=1/2 amplitudes is somewhat larger in
these decays than it is in other hyperon decays. At leading order there are two
operators responsible for the |Delta I|=3/2 parts of the Omega^- decays which
also contribute at one loop to other hyperon decays. These one-loop
contributions are sufficiently large to indicate (albeit not definitely) that
the measured width ratio of Omega^-->Cascade^0+pion^- to
Omega^-->Cascade^-+pion^0 = 2.7 may be too large.
