1. A simple technique of ‘rosette’ formation by low-density-lipoprotein-coated erythrocytes around human lymphoblastoid cells, stimulated to generate specific high affinity low-density lipoprotein receptors, is described. 2. Rosette formation is specific for high-affinity surface binding alone and the properties of the low-density lipoprotein receptors defined by it are identical with those found by using 125 I-labelled low-density lipoprotein binding at 4°C. 3. Preliminary observations suggest that specific surface binding of low-density lipoprotein is shown by some, but not all, lymphoid cell lines, is independent of certain other surface receptors and is unrelated to whether the cells originate from B or T cells. 4. Loss of low-density lipoprotein surface receptors on lymphoid cell lines (as with other surface receptors) may occur simply from prolonged culture rather than as a result of genetically mediated familial abnormality.