Glucose metabolism of respiratory and nonrespiratory muscles of different fiber composition was investigated in conscious rats. The accumulation of phosphorylated 2-deoxyglucose (2DGP) was increased in skeletal muscles by 56-102% and in diaphragm by 236% at 3 h after treatment with 100 micrograms/100 g endotoxin. The increase was still marked at 24 h, whereas it diminished at 48 h in the diaphragm, abdominal muscle, and white portion of the quadriceps. In the red portion of this muscle 2DGP accumulation was less than that in time-matched controls at 24 and 48 h. Whole gastrocnemius (mixed-fiber types) showed no changes after 24 h. The high 2DGP accumulation in brain remained stable. The retention of 2DGP in tissues, studied by sequential double labeling, did not change 3 h after endotoxin. The lumped constant was similar in the isolated epitrochlear muscles of endotoxemic and control rats. Whole-body glucose utilization (Rd) was increased by 68% 3 h after endotoxin, but it was normal at 24 and 48 h. The increase of glucose utilization by the entire skeletal muscle mass was responsible for approximately 25% of the increase in Rd; therefore it appears that other tissues also contributed significantly to the endotoxin-induced alterations in carbohydrate metabolism.