  We obtained high quality spectra of 135 stars of spectral types F and later
and derived ``overall'' broadening functions in selected wavelength regions
utilizing a Least Squares Deconvolution (LSD) procedure. Precision values of
the projected rotational velocity $v \sin{i}$ were derived from the first zero
of the Fourier transformed profiles and the shapes of the profiles were
analyzed for effects of differential rotation. The broadening profiles of 70
stars rotating faster than $v \sin{i} =
  45$ km s$^{-1}$ show no indications of multiplicity nor of spottedness. In
those profiles we used the ratio of the first two zeros of the Fourier
transform $q_2/q_1$ to search for deviations from rigid rotation. In the vast
majority the profiles were found to be consistent with rigid rotation. Five
stars were found to have flat profiles probably due to cool polar caps, in
three stars cuspy profiles were found. Two out of those three cases may be due
to extremely rapid rotation seen pole on, only in one case ($v \sin{i} = 52$ km
s$^{-1}$) solar-like differential rotation is the most plausible explanation
for the observed profile. These results indicate that the strength of
differential rotation diminishes in stars rotating as rapidly as $v \sin{i} \ga
50$ km s$^{-1}$.
