The electrochemical properties of LixFeS2 in a Li+ ion conductive glass were investigated. The electrode reaction shows two potential plateaus within the range 0 less than or equal to x less than or equal to 4, and is reversible. The reduction of FeS2 by 4e(-) or Li2FeS2 by 2e(-) did not proceed to form Fe metal as reported in earlier studies. LixFeS2 is promising as an electrode active material in a solid state lithium battery.