Effects of schisandrin B enantiomers ((+)Sch B and (–)Sch B) treatment on cellular reduced glutathione (GSH) level and heat shock protein (Hsp)25/70 production were investigated in H9c2 cardiomyocytes. (+)Sch B and (–)Sch B at 6.25 μM produced a time-dependent and biphasic change in cellular GSH level and Hsp25/70 production, with the stimulatory effect of (–)Sch B being more potent. The GSH- and Hsp-enhancing effects were accompanied by a parallel cytoprotection against xanthine oxidase/xanthine-induced toxicity, with the biphasic time course of (+)Sch B- or (–)Sch B-induced protection being superimposed with that of the increase in GSH level but not Hsp25/70 production. The results indicate that (–)Sch B produces more potent enhancing effects on cellular GSH and Hsp production as well as protection against oxidative injury than (+)Sch B in cardiomyocytes.