The chronic myelogenous leukemia-associated P210 BCR-ABL oncogene protein product has been produced using the baculovirus expression system. High-level expression of the P210 BCR-ABL protein required the removal of GC rich 5' non-coding sequences. P210 BCR-ABL synthesized in insect cells is an active tyrosine protein kinase indistinguishable from P210 BCR-ABL isolated from human cells. Both proteins utilize angiotensin II as a phosphate acceptor in vitro with a Km for ATP of approximately 1.5 microM. P210 BCR-ABL produced in insect cells undergoes autophosphorylation in vitro and in vivo. Gel filtration of P210 BCR-ABL reveals that the protein elutes as a high molecular weight complex of about 800 kD. Approximately 4 to 5 mg of P210 BCR-ABL is produced in one liter of infected insect cells. Following cell disruption and a three-step ion exchange and gel filtration purification procedure, 0.4 mg of soluble P210 BCR-ABL is obtained per liter of suspension culture. An alternative procedure employing detergent extraction and immunoaffinity chromatography gave higher yields and purity from smaller amounts of infected cell extracts. The availability of intact, soluble and enzymatically active P210 BCR-ABL represents a significant advance for studying the biochemical and biophysical properties of the ABL oncogene family of proteins.