p62c-yes, the protein product of the yes proto-oncogene, was found in association with a cellular protein of 38 kD in chicken cerebella. The complex was detected by immunoprecipitation of cerebellar membranes with affinity purified anti-yes IgG followed by in vitro phosphorylation of the immunocomplex. Both proteins were found to be phosphorylated exclusively on tyrosine. The sedimentation profile of the yes kinase indicated that a fraction of p62c-yes was complexed with the 38 kD protein and comigrated in the gradient with a molecular mass of approximately 150 kD. We have previously described the association of p60c-src with a 38 kD protein, referred to as p38 [Grandori, C. and Hanafusa, H., J. Cell Biol. (1988), 107: 2125-2135]. Comparison of the src-associated p38 with the yes-associated 38 kD protein indicates that they are indistinguishable by one-dimensional peptide mapping. Association of p38 with more than one member of the src-family of tyrosine kinases makes this protein an attractive probe to study the structural and functional aspects of these enzymes.