Hubble diagram of effective K‐ and stretch‐corrected m_B vs. redshift for the 11 SNe observed with WFPC2 and reported in this paper. Circles represent SNe in the primary subset (subset 1); the one point plotted as a cross (the very reddened supernova SN 1998aw) is omitted from that subset. Open circles represent reddened SNe omitted from the low‐extinction primary subset (subset 2), while filled circles are in both subsets 1 and 2. Top: No host galaxy E(B−V) extinction corrections have been applied. Inner error bars only include the measurement error. Outer error bars include 0.17 mag of intrinsic dispersion. Bottom: Extinction corrections have been applied using the standard interstellar extinction law. Error bars have been increased by the uncertainty in this extinction correction. Again, inner error bars represent only measurement uncertainties, while outer error bars include 0.11 mag of intrinsic dispersion. Lines are for three example cosmologies with the indicated values of Ω_M and Ω_Λ; the solid line is the best‐fit flat‐universe cosmology to our full primary subset with extinction corrections applied.