Persons who have developed acute flaccid paralysis following infection with wild-type polioviruses or vaccine-associated paralytic poliomyelitis usually excrete polioviruses for only a few weeks. However, some patients with paralytic poliomyelitis have had prolonged excretion of polioviruses for periods of up to 10 years after onset of disease. Most prolonged excretors have been identified in industrialized countries. We studied 348 patients 2-28 years old in Ethiopia, Pakistan and Guatemala with residual paralytic poliomyelitis to determine if they had IgA or IgG deficiency or persistent poliomyelitis excretion at least 1 year after onset of disease. None of the 348 affected individuals had IgG deficiency or persistent poliovirus excretion. One child had borderline low serum IgA concentration. Since we did not study children under 2 years of age, persons born with IgG deficiency disorders may have died in developing countries where replacement immunoglobulin therapy is not readily available. Nevertheless, persistent poliovirus excretion among persons 2 years of age and older with residual paralytic poliomyelitis is uncommon in developing countries.