Knowledge of signal transduction pathways has uncovered therapeutic targets for cancer. Based on genetic and biochemical studies of leukemia cells, inhibiting hyperactive Ras represents a rational therapeutic strategy for many hematologic malignancies. Because posttranslational processing by farnesyltransferase is essential for transformation by oncogenic Ras, specific inhibitors of this enzyme are being evaluated as cancer therapeutics. The authors review recent laboratory insights on farnesyltransferase biology and on the development of inhibitors, summarize preclinical and clinical data in myeloid malignancies, and briefly discuss other strategies of interfering with hyperactive Ras.