Lymphocyte death in peripheral blood of the mouse represents the death of both short‐ and long‐lived lymphocytes. The present data were based on lymphocyte separation, supravital dye exclusion, and autoradiographical procedures. The data strongly indicate that the frequency of intravascular cell death in the population of short‐lived lymphocytes is 4–10 times higher than the frequency of intravascular cell death of long‐lived lymphocytes.