The hydration structure of the bisulfide (HS-) ion in dilute aqueous solution was characterized by means of an ab initio quantum mechanical charge field (QMCF) molecular dynamics simulation at the Hartree Pock level employing Dunning double-c plus polarization function (DZP) basis sets. An average H S hood distance of 1.35 angstrom resulted from the simulation and a hydration shell located at 2.42 angstrom S-HS center dot center dot center dot H-w and 3.97 angstrom HS- distances, respectively. At the sulfur site, the average coordination number is 5.9 :1: 1.1, while the value for the hydrogen site is 9.2 +/- 1.6. The calculated HHS--S-HS- stretching frequency of 2752 cm obtained from the QMCF MD simulation is in good agreement with that reported from the Raman spectrum (2570 cm-(1)) only if a scaling factor of 0.89 is applied. The stability of the nondissociated HS- structure is reflected by the force constants of 436.1 and 4.5 N/m determined for the HHS--S-HS- and H-HS center dot center dot center dot O-w bonds. respectively. A weak structure-making effect of the hydrated HS- ion results from the mean residence times of 1.5 and 2.1 ps of coordinated water molecules at the sulfur and hydrogen sites of the HS- ion, respectively.