We have established that chemisorption of atomic hydrogen on Si(110)5×1 surface forms two distinct 1×1 phases depending on temperature during H exposure. The high temperature phase is found to be the monohydride phase, Si(110):H. The room temperature phase has additional orbital intensity in its electronic density of states, which we interpret as due to hydrogen atoms chemisorbed weakly at nontetrahedral sites in the selvedge. Numerical estimates of the amounts of H involved have been made. The change of LEEDpattern during H exposure suggests that the 5×1 superstructure is due to relaxation of surface Si atoms rather than due to surfacevacancies.