The correlation between transmembrane potential and the degree of cellular metabolic deterioration has been studied in skeletal muscle in dogs during shock. A shock model consisting of exteriorization of the intestine for 3 h, resulting in fluid loss, decrease in blood pressure and death 3–4 h after the replacement of the intestine, was used. During the exteriorization period and after the return of the intestine repeated skeletal muscle biopsies were taken for enzymatic fluorometric analyses of ATP, phosphocreatine, G-6-P, glucose and lactate. At the same time intervals transmembrane potentials of skeletal muscle cells were recorded by the use of a modified Ling-Gerard microelectrcde and skeletal muscle tissue pH was measured with a small glass electrode. The shock resulted in a progressive decrease in transmembrane potential from a mean initial value of -91 to -72 mV at the end of the studied 6-hour period. At the same time tissue pH decreased from 7.37 to 6.89. The total phosphagen content, taken as the sum of ATP and CP, decreased while glucose mobilization and lactate increase occurred. There was a highly significant (p < 0.001) linear relationship between transmembrane potential on the one hand, and tissue lactate as well as tissue pH on the other. The corresponding correlation to tissue phosphocreatine was also significant. Cellular deterioration as illustrated here by tissue pH, tissue lactate and tissue phosphagen levels is therefore sensitively reflected in changes of transmembrane potential in skeletal muscle.