The aim of the present study was to investigate the influence of some possible risk factors in development of ALL. A hundred and sixteen children diagnosed as ALL over a three year period in our institute were involved in the study. Their ages ranged between 1 and 14 years (7.35±3.8). Four hundred children without any malignant or chronic disorders served as the control group. Male sex, increased paternal age (over 40 years), presence of malignant disorders among close relatives, pesticide exposure and birthweight over 4 kg seemed to be the factors associated with increased risk of ALL in children.