  The distance to NGC 7331 has been derived from Cepheid variables observed
with HST/WFPC2, as part of the Extragalactic Distance Scale Key Project.
Multi-epoch exposures in F555W (V) and F814W (I), with photometry derived
independently from DoPHOT and DAOPHOT/ALLFRAME programs, were used to detect a
total of 13 reliable Cepheids, with periods between 11 and 42 days. The
relative distance moduli between NGC 7331 and the LMC, imply an extinction to
NGC 7331 of A_V = 0.47+-0.15 mag, and an extinction-corrected distance modulus
to NGC 7331 of 30.89+-0.14(random) mag, equivalent to a distance of 15.1 Mpc.
There are additional systematic uncertainties in the distance modulus of +-0.12
mag due to the calibration of the Cepheid Period-Luminosity relation, and a
systematic offset of +0.05+-0.04 mag if we applied the metallicity correction
inferred from the M101 results of Kennicutt et al 1998.
