A partial cDNA clone encoding the gene for human transforming growth factor-beta 1 (TGF-beta 1) was isolated from a human bladder carcinoma cell line (5637) cDNA library. Following restriction enzyme processing and ligation of synthetic oligonucleotide linkers, the gene was inserted into a plasmid and transfected into Chinese hamster ovary cells. Clonal selection and growth conditions resulted in a method for production of recombinant human TGF-beta 1 at 7 mg/liter in conditioned cell medium. Through a combination of low pH treatment, cation-exchange chromatography, and salt precipitation, the recombinant human TGF-beta 1 was purified in milligram amounts to > 95% purity in a yield of about 36%. Purification to homogeneity was accomplished by chromatography on C18 silica gel. Amino acid analysis, N-terminal sequencing, and growth inhibition assays indicate identity with the molecule from human platelets.