The clinical and immunological features of 14 patients including 12 with selective and two with partial IgA deficiency are presented. One patient was asymptomatic, six patients had allergic diseases, three patients had hematologic disorders and the remaining patients had chronic-recurrent infections. The IgG and IgM serum concentrations were high in four and two patients, respectively. Delayed hypersensitivity skin tests were applied to seven patients, and were found positive in all. E-rosette forming cells were within the normal range. In vitro lymphoblastic transformation with PHA was normal in all the patients, except for one. Two patients had no sIgA+ B cells. The percentage of CD+4 T cells was decreased in one patient and the percentage of CD+8 T cells was increased in another, both of whom had a low CD4/CD8 ratio. The heterogeneity of clinical and immunological features in these patients suggests that various mechanisms may be responsible for the immunopathogenesis of IgA deficiency.