Objective To find out some trigger factors for the onset of acute childhood leukemia by examining seasonal distribution through a small cohort study in a single center.Methods The records of 688 childhood patients(age≤15 years)whom were initially diagnosed at Blood Disease Hospital of CAMS from October 2003 to June 2006,were retrospectively analyzed.Results In terms of time,our study provides modest support for sessonal peaks in summer and winter,or in Jan & Jun.Conclusion We initially realized the season tendency of the onset of acute childhood leukemia in some northern parts of China.which suggest that childhood acute leukemia is associated with the infection.