  We present the results of an intensive ground-based spectrophotometric
monitoring campaign of the Seyfert galaxy NGC~4151 for a period of over two
months, with a typical temporal resolution of one day. Light curves for four
optical continuum bands and the H$\alpha$ and H$\beta$ emission lines are
given. During the monitoring period, the continuum at 6925~\AA\ varied by
$\sim$17\% while the continuum at 4600~\AA\ varied by $\sim$35\%, with larger
variations in the near UV. The wavelength dependence of the variation amplitude
also extends into the far UV. The dependence in the 2700$-$7200~\AA\ range can
be explained by the different relative starlight contributions at different
wavelengths, but the large variability at 1275~\AA\ cannot be explained in this
way. The continuum variability timescale is of order 13 days and is similar at
all optical wavelength bands. No evidence for a time lag between the optical
continuum and the UV continuum and emission lines was found. The H$\alpha$
emission line flux varied by about 12\% with a gradual rise throughout the
campaign. Its cross correlation with the continuum light curve gives a lag of
$0-2$ days. The variations in the H$\beta$ emission line flux are about 30\%
and lag the continuum by 0$-$3 days. This is in contrast to past results where
a time lag of 9$\pm$2 days was found for both emission lines. This may be due
to a different variability timescale of the {\em{ionizing}} continuum, or to a
real change in the BLR gas distribution in the 5.5 years interval between the
two campaigns.
