Biochemical properties of the heat shock or stress proteins of mammalian cells have been investigated using two-dimensional gel electrophoresis and immunological techniques. Of the major mammalian stress proteins (Mr = 72,000, 73,000, and 90,000) and minor stress proteins (Mr = 80,000, 100,000, and 110,000), the 80- and 90-kDa proteins were found to be phosphoproteins in all cell types examined. The 100-kDa protein was found to incorporate phosphate in only some cell types examined. In studies of the metabolic incorporation of mannose into the stress proteins, only the 100-kDa protein was found to be a glycoprotein. Two of the stress proteins, the 80- and 100-kDa species, were found to be identical with the proteins induced in cells grown in the absence of glucose (i.e. the "glucose-regulated proteins"). These same two proteins also were induced in cells treated with the calcium ionophore A23187. To begin examining the intracellular location of these multiregulated proteins, immunofluorescence microscopy studies were carried out using a monoclonal antibody against the 100-kDa stress protein. The antigen was localized primarily with the Golgi apparatus and less prominently with the plasma membrane and nucleus. Heat shock treatment resulted in an increased number of the cells exhibiting a nuclear location of 100 kDa.