Human tumors and tumor cell lines were analyzed for the presence of mRNA coding for transforming growth factors alpha and beta (TGF-alpha and -beta) and the epidermal growth factor receptor. TGF-alpha mRNA was not detectable in hematopoietic tumor cell lines but was found in a variety of solid tumor cells, particularly carcinomas. Many of the tumors that contained TGF-alpha mRNA also expressed high levels of epidermal growth factor receptor mRNA. The concentration of TGF-alpha in the media of several tumor cell lines did not necessarily correlate with TGF-alpha mRNA levels, as a substantial fraction of TGF-alpha can remain cell associated. The levels of TGF-beta mRNA in tumor cell lines and tumor specimens were variable, but higher in tumors than in the adjacent normal tissues.