Twenty-six patients with active and inactive sarcoidosis were studied. Surface immunofluorescence techniques with polyvalent and monospecific antisera after resynthesis of intrinsic Ig, were employed to determine the number of B cells. The peroxidase positive cells were not included in the count. Percentage and absolute number of lymphocyte forming rosettes with mouse erythrocytes were also determined. Compared to normal controls the numbers of SmIg positive cells were practically unchanged. Moderate decrease in the absolute number of mouse rosette forming cells was found in active disease. Our results will be correlated with the staging of the disease.