Induction treatment was stratified by age and initial WBC count. Patients ≤65 years of age with a WBC count less than 5,000/µL were randomized to receive the reference ATRA treatment of our previous trial (APL91 trial) {Fenaux, 1993 #2088}, ie, 45 mg/m2/d ATRA followed by CT (ATRA→CT group) or ATRA plus CT (ATRA+CT). In the ATRA→CT group, patients received 45 mg/m2/d ATRA orally until CR, with a maximum of 90 days. After CR achievement, they received a course of 60 mg/m2/d daunorubicin (DNR) for 3 days and 200 mg/m2/d AraC for 7 days (course I). However, course I was added to ATRA if the WBC count was increased to greater than 6,000/µL, 10,000/µL, or 15,000/µL by day 5, 10, and 15 of ATRA treatment, respectively, be-cause, from our experience, patients were at risk of ATRA syndrome above those thresholds{de Botton, 2003 #1127; De Botton, 1998 #1604}. Patients randomized to the ATRA+CT group received the same combination of ATRA and CT, with course I of CT starting on day 3 of ATRA treatment.