We propose to observe high J rotational and rot-vib lines of sulfur-bearing molecules in active star-forming molecular clouds. Chemical reactions leading to the formation of sulfur compounds are highly endothermic and several observational and theoretical studies have suggested that sulfur bearing molecular species may be unique tracers of warm gas in interstellar shocks and/or photon-dominated regions in dense molecular clouds in star-forming regions. Our observations will provide new information about the physical conditions in the shocks and photon-dominated regions (PDRs) in which sulfur species become abundant. By comparison with model calculations of excitation and chemical processes we will be able to determine the density, column density, temperature and abundance of the sulfur-bearing species. The observation of sulfur compound lines is not part of the central central program projects. The proposed observations will complement the central program (MPEWARM Drapatz et al.) data of shocked and photon dominated regions.