Somatic mutation of nucleophosmin gene (NPM1) has been reported inacute myeloid leukemia (AML). In the present study, NPM1 mutation wasinvestigated by reverse transcriptase-PCR (RT-PCR) in 27 patients with de novoAML as well as 10 normal subjects as a control group. Internal tandem duplicationmutation of Fms-like tyrosine kinase 3 (FLT3/ITD) and length mutation of FLT3(FLT3/LM) were also analyzed. NPM1 mutation was detected in 44.4% of patientswhile FLT3/ITD was detected in 62.9% and FLT3/LM in 14.8%. All the controlsubjects were negative for the three types of mutation. NPM1 positive patientswere older in age and had higher mean total leucocytic count than NPM1 negativepatients but the difference did not reach a statistically significant level. NPM1mutation was seen in AML FAB subtypes M1, M3, M4, and M5 but was absent inM2. It was highly significantly associated with AML FAB M4 and significantlyassociated with CD-14, lymphadenopathy and FLT3/ITD mutation. The highestremission rate was achieved in the NPM1 mutated FLT3/ITD negative patients.Thus, it can be stated that NPM1 is a common mutation in AML and it is apredictor for better response to induction therapy only in the absence of FLT3/ITD.