We identified ret oncogene products in NIH 3T3 cells transformed by the ret oncogene (NIH(ret)) and a cell line (Lym-ret) established from pre-B cell lymphoma which developed in E mu-ret transgenic mice. Using the polyclonal antibody against the kinase domain of ret, two glycoproteins with apparent molecular weights of 100 kd and 96 kd were found in both cell lines, although the expression level of the 100 kd protein was much higher than that of the 96 kd protein. Cell fractionation experiments indicated that the 100 kd protein was present predominantly in the membrane fraction while the 96 kd protein was found in both membrane and cytosol fractions. Western blot analysis indicated that the 100 kd ret protein was phosphorylated on tyrosine residues in vivo.