OH-(H2O)(n) and SH-(H2O)(n) (n=1-5) clusters have been studied using ab initio calculations. The relative stabilities of various isomers of SH-(H2O)(n) are quite different from those of the corresponding isomers of OH-(H2O)(n) (n=3-5) at 0 K, and are almost the same as those of the corresponding isomers of OH-(H2O)(n) at 298 K. That is, the relative stabilities of various isomers of SH-(H2O)(n) and OH-(H2O)(n) at 298 K are quite different from those at 0 K due to the entropy effect. The ionization potential, charge-transfer-to-solvent energy, and OH stretching vibrational spectra are reported to facilitate future experimental work.