SummaryThe aim of this study was to compare the E rosette-forming cells and nonspecific alpha naphtyl esterase (ANAE)-positive lymphocyte values in normal and pathologic situations. In newborns, the ANAE-positive lymphocytes represented less than 60% of the E rosette population. During the first year of life, E rosette-forming cells (E-RFC) reached normal values as soon as one month whereas only three-fourths of the T cells exhibited an ANAE-positive staining. In adult T cell populations, nearly 90% were ANAE-positive. Our observations of immune deficiencies suggested that the relative proportions of E-RFC and ANAE-positive lymphocytes were generally comparable to normal values. However, in the majority of the patients with very low or absent E-RFC (severe combined immune deficiencies, Di George syndrome, and congenital rubella), some ANAE-positive lymphocytes could be detected. Our immunologic survey shows that the ANAE-positive lymphotytes were in a normal range 2 years after a bone marrow transplantation in severe combined immune deficiencies patients. One child who exhibited a normal amount of E-RFC and whose lymphocytes failed to respondin vitroto mitogens had practically no ANAE-positive lymphocytes. An elevated amount of ANAE-positive cells in juvenile rheumatoid arthritis may reflect an augmentation of the T helper functions which permanently stimulatedin vivoimmunoglobulin production.