AbstractMany of the present concepts in lymphocyte physiology were established using experimental protocols involving surgery in cortico‐sensitive rodents. In the present report we demonstrate that commonly used operative procedures in mice result in a depletion of 50‐90% of cells from primary or secondary lymphoid organs 24 to 48 h post‐ surgery. Adrenalectomy, by itself, induces considerable depletion, and does not abolish the effects of stress in lymphocyte populations. These findings indicate that questions concerning the dynamics of production renewal rate and life‐span of lymphocytes cannot be investigated by approaches involving surgery in the mouse.