A RNA-directed DNA polymerase was partially purified from a human homologous, mixed mesodermal sarcoma by DEAE-cellulose chromatography after sucrose density centrifugation. The enzyme transcribed poly(rA) most effectively but also transcribed poly(rI), poly(dA) and poly(rG) and to a lesser extent, poly(rmC). It was unable to transcribe poly(rU). The product with poly(rA) as template contained large material (greater than 28S) in addition to some proper size product demonstrating a slippage reaction. This pattern of transcription, while similar to avian myeloblastosis virus DNA polymerase, reveals qualitative differences making direct extrapolation from studies with animal oncornaviruses to human cancer difficult. In this paper, the detection and purification of RNA-directed DNA polymerase from a patient with an uncommon uterine sarcoma is reported along with the template specificities of the enzyme.