T cells and T cells subsets in peripheral blood of patients with different forms of pulmonary tuberculosis were evaluated to explain some aspects of the immunocompromised state of these subjects. Diagnosis was made by baciloscopy (BAAR), chest roentgenography i.d.r Mantoux, and other clinical analysis. Spontaneous E-Rosette test (RE) was used to quantify Total (RET 4ºC) and Active T cells (REA 37ºC) and the same test after incubation with Theophilline (The) for helper cells (The-re-sistant cells: RETR) and suppressor cells (The-sensitive cells: RETS). Patients were followed for at least 4 months after therapy. The data demonstrate a significant decrease of relative and absolute numbers of Total T-cells and a diminished T helper/T suppressor subset ratio (RETR/RETS) which dropped to less than 1 in untreated patients. Treated patients with a favourable evolution showed a restoration of Total active and helper T cells. RETR/RETS ratio was also significantly increased. In patients with highly positive BAAR, low on negative i.d.r Mantoux, a decreased level of immunocompetent cells was observed. The 3 aspects were associated. Nutritional condition of the patients wal also associated with the predisposition to acquire this disease.