The frequency of major immunoglobulin isotype and IgG subclass deficiencies among 74 children aged six months to 14 years with recurrent infections was studied. All children had at least five to six episodes of respiratory tract infections, while recurrent diarrhea had occurred in eight. Two selective and six partial IgA deficiencies were detected. IgG4, IgG3 and IgG2 deficiencies, either isolated or combined, were found in 13, nine and one patient respectively. Among these there were two combined deficiencies of IgA + IgG4, three of IgA + IgG3, one of IgA + IgG2 + IgG4, one of IgG1 + IgG3 and two of IgG1 + IgG4. There was one patient with panhypogammaglobulinemia. Our results, similar to those of other studies, showed that the occurrence of the Ig isotype, particularly subclass deficiencies, is not uncommon in children with frequent infections.