Acute myeloid leukemia, the most common form of acute leukemia in adults, is a clinically and molecularly heterogeneous disease that is curable in about 30% of cases. It is defined as uncontrolled proliferation of cells of the myeloid lineage. Today it is well appreciated that the availability of markers for monitoring and quantitating MRD in hematological CR is of major clinical importance and helpful in planning treatment in individual patients with AML. Published data suggest that serum tryptase levels are elevated in a group of patients with AML. In these patients, the enzyme is produced in AML blasts and reflects the burden of leukemic cells. In addition they showed that tryptase is useful for quantitation and monitoring of minimal residual AML. The present study assessed mast cell tryptase gene expression using RT-PCR.