  We have compared the risetime for samples of nearby and high-redshift type Ia
supernovae (SNe Ia).
  The fiducial risetime of the nearby SNe Ia is 2.5+/-0.4 days longer than the
proemial risetime determined by Goldhaber (1998a,b) for high-redshift SNe
  Ia from the Supernova Cosmology Project.
  The statistical likelihood that the two samples have different fiducial
risetimes is high (5.8 sigma) and indicates possible evolution between the
samples of SNe Ia. We consider the likely effects of several sources of
systematic error, but none of these resolves the difference in the risetimes.
  Currently, we cannot directly determine the impact of the apparent evolution
on previous determinations of cosmological parameters.
