Use of DEAE-dextran (a polycation) increases and stabilizes the rosettes formed between sheep red cells and human peripheral blood lymphocytes. Under its influence, reproducible stable rosettes are formed after one hour of incubation in an ice bath instead of the usually required 18 to 24 hours. We have shown that rosettes are specific for T-cells and not due to "co-rosetting" of nonrosette forming cells into the T-cell rosette clusters. Only the cells from normal controls consistently show an increase in rosette formation hence routine use of this 'stabilizer' in clinical immunology is not recommended.