AN abnormal T4 : T8 lymphocyte ratio has recently been reported in the cervical epithelium of patients with cervical intraepithelial neoplasia (CIN). This study examined T lymphocyte ratios in the peripheral blood of 16 patients with CIN. Nine of the 16 patients had less than 40% T4 lymphocytes and the T4 : T8 ratio was inverted in 7 (44%). Similar but more profound lymphocyte abnormalities occur in the acquired immunodeficiency syndrome (AIDS). This is of interest because both CIN and AIDS are associated with viral infections, sexual intercourse and immunosuppression.