The T-lymphocyte subsets of 38 patients with chronic aplastic anemia (CAA) were measured by monoclonal antibody (McAb) and ABC method and the relationship of T-lymphocyte subsets and symptom complex groups by traditional Chinese medicine theory were also analysed. It was shown that the T subsets of patients with CAA have remarkable changes: Ts (41.3 +/- 11.2%) increased more than the control (22.9 +/- 4.5%), Th/Ts decreased significantly more than the normal control (0.98 +/- 0.38 to 1.59 +/- 0.38). From the group of deficiency of both vital energy and blood to the group of deficiency of Kidney-yang to the group of deficiency of Kidney-Yin to the group of deficiency of both Kidney-Yang and Kidney-Yin, the Th lymphocyte gradually decreased, Ts lymphocyte successfully increased (from 33.8 +/- 7.9% to 57.7 +/- 7.5%), Th/Ts ratio declined (from 1.29 +/- 0.36 to 0.57 +/- 0.19). The Th/Ts ratio of the latter two groups decreased more than the former two groups (P less than 0.01). These results indicated that the T lymphocyte subsets and symptom complex group of patients with CAA were closely related and when deficient Yang affects Yin the immunologic function of body has a more obvious change. This revealed the connotation of Kidney-Yin and Kidney-Yang on the immuno-regulating cells (T lymphocyte subsets) level.