The proposed cryofixation technique uses a tubule-shaped needle chilled in liquid propane for simultaneous excision and freezing of a tissue specimen. Due to this simultaneity, ionic shifts created by traumatic influences are avoided even in the outermost cells of the specimen. Moreover, it is shown here that stopping the blood flow for more than about 10 s results in notable ionic shifts between cells and extracellular space in rat heart and liver. Such preparative ischaemic injury is minimized by the Fast Cryofixation Technique because it can be easily performed on organs within the circulatory system, whilst the heart of the animal is still beating. Intracellular concentrations of the monovalent ions in rat heart and liver, obtained by this method, tally well with recent results from different independent techniques reported in the literature. As demonstrated by cross-sectioning and freeze-fracturing, the structural preservation of the freezing technique is sufficient for X-ray microanalytical work.