AbstractThis paper describes a therapeutical trial by oral administration of secretory IgA to an agammaglobulinemic patient with chronic polivirus infection.The patient developed paralytic polimoyelitis 18 months after the second poliovaccination, and continued to shed non‐vaccine‐like type 2 poliovirus for almost 2 yars after the onset of illness, although his clinical illness was not progressive. The patient lacked coproantibody response against poliviruses type 1, 2 and 3. From the standpoint of public health, the purified S‐IgA prepared from human colostrum which contained neutralizing antibody against type 2 poliovirs was given orally to the patient by the daily does of 150 mg for 7 days. The amount of fecal virus was reduced after the treatment and the fecal shedding of the virus ceased 2 months later, namely, almost 2 years after the onset of paralysis and 3 years and 5 months after the second vaccination.This case suggests that the oral administration of secretory IgA might be effective and advisable as a part of replacement therapy in various types of immune defficiencies associated with reduced secretion of IgA, especially for the management of persistent infection of enterovi