Frozen biological specimens from which water has been removed by etching show little or no charging when examined by scanning electron microscopy whereas the opposite occurs when etching is not carried out. Using gels containing known quantities of various electrolytes as a model, the resulting effect on X-ray microanalysis has been examined. At low accelerating voltages (5–15kV) high charging was obtained with frozen and hydrated specimens at temperatures of −140°C to −150°C. Under these conditions the X-ray spectra changed with total irradiation time; the signal from the specimen greatly decreased while that from the aluminium support stubs rapidly increased. When such specimens were coated with carbon there was little or no charging and the X-ray spectrum remained constant. A close correspondence was obtained between the results obtained by X-ray microanalysis and the known composition of elements, both qualitatively and quantitatively, of the coated, frozen and hydrated gels at temperatures below −100°C.