The extent of cellular deterioration around a high-velocity missile injury was studied in canine skeletal muscle biopsies. The tissue levels of high-energy phosphates and glycolytic metabolites were analyzed in four zones surrounding the bullet tract and in an uninjured extremity. Incorporation of leucine into skeletal muscle proteins in vitro in the different zones was determined. In the tissue adjacent to the bullet tract ATP and phosphocreatine (CP) decreased significantly and remained low. No significant changes of ATP and/or CP occurred in the other zones or in the control muscle. Lactate and glucose levels increased in all zones but G6-P levels decreased in the three zones close to the wound indicating anaerobiosis and disturbed utilization of glucose. Incorporation of leucine decreased in the innermost zone and no restoration took place, but more peripherally a certain reversible decrease was seen. The present results indicate that irreversible cell damage will occur in the tissue adjacent to a high-velocity bullet tract. Reversible cellular dysfunction may occur in tissues without gross changes.