  We have carried out a survey toward the central regions of 85 starless cores
in HCN J = 1-0 to study inward motions in the cores. Sixty-four cores were
detected with HCN lines. The infall asymmetry in the HCN spectra is found to be
more prevalent, and more prominent than in any other previously used infall
tracers such as CS J = 2-1, DCO+ J = 2-1, and N2H+ J = 1-0. We found close
relation between the intensities of the HCN and N2H+ lines. This implies that
the HCN is not much depleted in the central regions of the cores. In some
cores, the HCN spectra show different sign of asymmetry from other molecular
lines. A few cores show various signs of asymmetry in individual HCN hyperfine
lines. The distribution of the velocity shift dV of the HCN profiles with
respect to the systemic velocity of the optically thin tracer is found to be
more shifted toward bluer side than those of other infall tracers, indicating
that the HCN traces inward motions more frequently. The dV distribution of each
HCN hyperfine line for all sources is similar. Moreover the dV values obtained
from different HCN hyperfine lines for each source are nearly similar. These
may mean that most of starless cores are in similar kinematic states across the
layers of the cores. We identify 17 infall candidates using all available
indicators such as the velocity shift dV and the blue to red peak intensity
ratio of double peaked profiles for HCN J = 1-0, CS J = 2-1, J = 3-2, DCO+ J =
2-1, and N2H+ J = 1-0. Four of them, L63, L492, L694-2, and L1197 are found to
show higher blue to red ratio in the HCN hyperfine line along the lower
opacity, suggesting that infall speed becomes higher toward the center.
