The shedding and resynthesis of Fc, C3 receptors, and receptors binding SRBC has been studied in normal peripheral lymphocytes, in lymphocytes from CLL patients and in a Raji cell line during 4 h incubation at 37 degrees. During the first part of the incubation, an increased release of receptors was observed. The shed, functionally active, receptors were detectable in the incubating medium on the basis of their ability to inhibit rosette formation specifically. After 4 h incubation the original ratios of the different rosette forming cells were observed, showing that the cells were capable of resynthesizing their shed receptors. This later phenomenon may be the result of an active metabolic process. The shedding was not detectable on Raji cells. Different patterns of receptor shedding and resynthesis were demonstrated by the lymphocytes of CLL patients. The correlations between the reappearance of the receptors on the cells, and the metabolism of the lymphocytes, is discussed.