Acute respiratory infection (ari) is the main cause of morbidity and mortality in child under five years old. the prevalence of ari in banda aceh in 2010 is about 51,60%. exlusive breastfeeding is one of the way to prevent acute respitratory infection. coverage of exclusive breastfeeding administration in banda aceh in 2010 is 11,40%. this research is aimed to learn the the corelation between exlusive breastfeeding and the occurance of acute respiratory infection in child under five years old. method that is used in this research is cross sectional. sample was chosen by non probability sampling (accidental sampling) technique. the data was obtained by interviewing 71 mothers of child under five years old with quessionare and by reviewing patient’s status in kuta alam public health center in banda aceh from 20th february to 7th march 2012. data wa analyced by using bivariat method that is chi square. the result shows that p=0,029 (