Chronic exposure of the gray, short-tailed opossum, Monodelphis domestica, to ultraviolet radiation (UVR) induces highly vascularized mesenchymal tumors of the cornea. Cell lines derived from these UVR-induced corneal tumors and the corneal tumors themselves were examined for the presence of mRNA coding for basic and acidic fibroblast growth factors (FGF), transforming growth factors-beta and -alpha (TGF-beta and TGF-alpha), epidermal growth factor (EGF), and tumor necrosis factor-alpha (TNF-alpha). Basic FGF was expressed in the cell lines derived from corneal tumors and in the corneal tumors. Expression of basic FGF was high in one corneal tumor. Transcripts for acidic FGF were detected only in the corneal tumor cell lines, not in primary tumors. TGF-beta expression was detected in the corneal tumors and tumor-derived cell lines. TGF-alpha, EGF, and TNF-alpha transcripts were not detectable in any opossum material; however, homologous gene sequences for TGF-alpha and EGF were detected on Southern blots of opossum genomic DNA. Southern blot analysis revealed no evidence of amplification or rearrangement of the genes for basic FGF or acidic FGF in the UVR-induced corneal tumor that expressed high levels of basic FGF. Opossum basic FGF, which stimulated the proliferation of fetal bovine heart endothelial cells, was purified by heparin affinity chromatography from a UVR-induced corneal tumor and a corneal tumor cell line. Immunoblotting of opossum basic FGF from a corneal tumor cell line using antiserum to bovine basic FGF showed two prominent immunoreactive bands of 17.5 and 18.5 kDa. Expression of basic FGF and acidic FGF may play a role in the development and progression of UVR-induced corneal tumors in M. domestica