The effect of 24 h food deprivation on endotoxin (ET) lethality in SpD rats was studied. Fed and fasted animals received either 6 h i.v. infusions or i.p. boluses of ET at low, intermediate and high doses, and survival for seven days observed. Fasting was associated with 208-240% greater mortality when ET was infused i.v., and 87-200% when given i.p. ET doses LD10-LD80 gave a linear relationship with mortality. In non-fasted control rats liver glycogen content reduced by 1.28 mumols/min/g dry liver wt over the first post-prandial six hours, and increased by 65-99% in a dose dependent manner after ET (p less than 0.01). Evidence was also obtained relating both liver damage (assessed blind by histopathological scoring) and leucopenia with endotoxin dose, results which were modified by nutritional status. The evidence supports the role of liver glycogen as a protective substrate resource in endotoxic shock.