To date the most accepted definition of sepsis includes the suspicion of infection plus the systemic response to it (tachypnea, tachycardia and hypothermia or hyperthermia). This condition could lead to the so called multiple organ failure syndrome (MOFS) when there are evidences of flinctional compromise in two or more systems. Muscle weakness and wasting are common findings in those patients. The skeletal muscle histopathology in patients with those two conditions has been poorly studied. The only electron microscopic investigation we could find describes alterations in muscle fibers and endplates.In this work we describe the whole spectrum of changes found in skeletal muscle of patients suffering from sepsis and MOFS.Five patients recluded in an Intensive Care Unit were selected, two had a diagnosis of sepsis, and three presented MOFS. Needle muscle biopsies from quadriceps femoris muscle were obtained. Tissue samples were processed with routine techniques for transmission electron microscopy and observed in a Hitachi H-500 electron microscope.