This paper is to report the determination of the skeletal muscle cellular membrane potential (SMCMP) in vivo with the technique of "Semi-floating"glass microelectrode. The changes of SMCMP and the distribution of extra- and intracellular electrolytes and water in different phases of irreversible hemo-rrhagic shock in rabbits were studied systematically.It was found that SMCMP decreased significantly and immediately as soon as hypotension occurred, which means that the functions of the cellular membrane begin to deteriorate in the early stage of shock; SMCMP continued to decrease when the shock was progressing, which reflects that besides the failure of the cellular membrane function, there is also the degradation of the functions of the cell proper; the leakage of the intracellular potassium across the cellular membrane and the retention of the intracellular sodium and water occurred three hours after the onset of the shock, which indicates that the inability of cells to regulate their volume.