To determine the pharmacological potential of penfluridol against AML cells, we investigated the effects of various concentrations (1.25~40 μM) of penfluridol on the growth of three human AML cell lines, HL-60 (FLT3-WT), U937 (FLT3-WT), and MV4–11 (FLT3-ITD), for 24 and 48 h using an MTS assay. The gene discussed is FLT3; the disease is acute myeloid leukemia.