frozen aqueous suspensions can be observed under good conditions when the specimen is vitrified. The contrast then obtained from embedded particles is low but measurable. It can be quantitatively controlled by adjusting the composition of the solution if partial evaporation is prevented. When this is the case, contrast measurements remain within 20% of the theoretically predicted values. Three aspects of electron beam damage at low temperatures are described: (1) Beam-induced transformation of cellulose nitrate into crystals, probably of N2O. (2) Realization of mass loss of warming organic specimens irradiated at low temperature. (3) Bubbling in vitreous ice.