An experimental shock model with rabbits and dogs was used (bleeding to an constant systemic pressure of 5.3-6.6 kPa) to investigate quality and time dependency of intra-extracellular gradients of Na+, K+ and Ca++ in skeletal and heart muscle. We found the ion gradient changes to be earlier and more pronounces in skeletal than in heart muscle, where strongest changes appear within the heart ears and significant smaller ones within ventricular and papillar muscles. Unexpectedly there was in heart and skeletal muscle the same two phasic ionic course, and a close correlation between ion gradient changes and shock duration in skeletal muscle. There is a good agreement between our results and the common clinical observations of ventricular arrhythmia caused by acute hypotonic circulatory situation and therefore the early restoration of the disturbed transcapillary exchange in the peripheral circulation is demanded.