Using a variable-temperature ultrahigh vacuum scanning tunneling microscope, we have studied the adsorption characteristics of H2S on Si(lll)-(7 x 7). The data suggest that H2S adsorbs dissociatively at submonolayer coverage, from 50 to 300 K, with HS bonded to an adatom and H bonded to a rest atom. The adsorption is site selective, and the adsorption site preference is temperature dependent. At 50 K, the faulted center sites are most favored for adsorption, followed by unfaulted center sites, faulted corner sites, and unfaulted corner sites. As the temperature is increased, the differences between the faulted and unfaulted halves diminish, but the center sites remain more reactive than the corner sites. At room temperature, the ratio of adsorbates on center sites versus corner sites is 2:1. We present an explanation to account for the non-langmuir kinetics involved in this system.