Cells transformed by acute transforming viruses of feline origin which differ in cellular acquired sequences were used to examine the effect of v-fes and v-fms gene on both the production and biological activity of transforming growth factors (TGFs). Cell cultures nonproductively transformed by the Snyder-Theilen and Gardner strains of feline sarcoma virus (FeSV), both of which contain the v-fms gene product release a small (10,000 Mr) and large (20,000 Mr) form of TGF. Both size classes TGF compete with EGF for EGF membrane receptors and stimulate anchorage-independent cell growth and thus resemble sarcoma growth factor (SGF) and TFGs released by human tumor cells. Snyder-Theilen FeSV-transformed cultures which contain a polyprotein associated tryosine specific protein kinase consistently release the highest liters of TGF (approximately 200 ng/l of cell culture) relative to all transformants examined. In contrast, cells transformed by McDonough FeSV (v-fms gene) which lack detectable kinase activity produce low levels of TGF (less than 10 ng/l). Large scale production of Snyder-Theilen transformed cell culture supernatants currently provide a rich source of transforming growth factor for use in primary sequence studies.