Recurrent and chronic infections in children are one of the most common reasons for physicians' visits that make a diagnostic challenge to pediatricians. Although the majority of referred children with recurrent infections are normal, underlying causes of recurrent infection such as atopy, anatomical and functional defects, and primary or secondary immunodeficiency must be considered in evaluation of children with this complaint.Although primary immunodeficiency diseases (PIDs) were originally felt to be rare, it has became clear that they are much more common than routinely appreciated. Early and accurate detection of PIDs in children is essential to institute early lifesaving care and optimized treatments. Therefore in the approach to children with recurrent infections, careful medical history taking and physical examination with more attention to warning PIDs signs and symptoms are essential to distinguish those children with underlying PIDs from those who are normal or having other underlying disorders. If indicated, appropriate laboratory studies including simple screening and advanced tests must be performed.