Nilotinib is a novel, highly selective oral Bcr-Abl inhibitor which is approximately 30-fold more potent than imatinib. High response rates with nilotinib were observed in all CML phases post imatinib failure. We evaluated the efficacy of nilotinib in newly diagnosed Ph-positive CML-CP. Thirteen patients with newly diagnosed Ph-positive CML-CP were treated with nilotinib 400 mg orally twice daily. The median age was 49 years (range, 24–72 years). The Sokal risk at pretreatment was low in 10 patients, intermediate in 2, and high in 1. The median follow-up is 8 months (range, 3–12 months). All patients have reached the 6-month evaluation. The rate of complete cytogenetic response [CGCR] (Ph 0%) at 3 and 6 months was 93% and 100%, respectively. This is compared with a CGCR at 3 months of 37% and with imatinib 400 mg/d and 61% with imatinib 800 mg/d (p=0.0002) and 54% and 85% at 6 months, respectively (p<0.0001), in historical data of newly diagnosed patients treated in studies at M. D. Anderson. Six patients were evaluable at 9 months and all were in CGCR. The median QPCR with nilotinib at 3, 6, and 9 months were, respectively, 3.4% (range, 0.02–29.5%), 1.8% (range, 0.004–9.13%), and 0.54% (range, 0.04–1.28%). At 3-month follow-up, major molecular response (BCR-ABL/ABL ratio<0.05%) was observed in 1/13 patients (8%) and in 6/11 (55%) at 6-month. Grade 3–4 myelosuppression was observed in 3 of the 13 patients and other grade 3–4 side effects in 3 patients (increased lipase in 2 and musculo-skeletal pain in 1). Four patients had their dose reduced to 400 mg daily due to extramedullary toxicity. Two patients were taken off after 6 and 8 months (patient choice) and switched to imatinib. In conclusion, early results with nilotinib 400 mg orally twice daily suggest significant efficacy manifested by complete cytogenetic responses in nearly all patients as early as 3 months after the start of therapy with a favorable toxicity profile.