The most common form of childhood cancer is leukemia, Calculation for more than one third of all childhood cancers among those ages 1 day – 14 years. The diseases of leukemia are worldwide, it occurred in both genders from male and females and in all age. A total of 80 different samples of patient children were collected from the central teaching hospital of pediatric in Baghdad. Obtained during the period from 1st Sept. 2019 till the 31 th of Aug. 2020. Each isolates identification by using Vitek 2. Isolated organism in leukemic children show 18 (22.5 %) gram positive and 62 (77.5 %) gram negative from the total sample 80 (100.0 %). The percent of male is 45 more than female which represents 35 in most age groups between age (1 day-3 year) 33 (100.0 %). In most distribution of organism according to the type of sample for gram positive is Staphylococcus aureus 13 (16.2 %) and gram negative Escherichia coli 21 (26.3 %), Klebsiella pneumoniae 13 (16.2 %), Pseudomonas aeruginosa 11 (13.8 %) from the total results 80 (100.0 %). In conclusion, the gram negative bacteria is more than gram positive bacteria and especially effect with Escherichia coli, and Staphylococcus aureus, in males for the age group 1 day to 3 years. And the most antibiotic sensitive to Escherichia coli is Imipenem, Amikacin, Gentamycin, Piperacillin/ Tazobactam and resist to Cefotazidime, Tobramycin, Cefepime, Ceftriaxone, Ciprofloxacin and Staphylococcus aureus most sensitive to Vancomycin, Gentamycin, Clindamycin, and resist to Penicillin, Cefotaxime, Ceftriaxone, Oxacillin.
