Cell-mediated immune response was evaluated in 150 patients with histologically confirmed bronchopulmonary carcinoma using bacterial and fungal recall antigens injected intradermally (PPD, candida, trichophyton). In the study group negative skin test reaction was found in 51 of 150 patients (34.0%), whereas in the control population it was found in 5 of 33 cases (15.1%) (p less than 0.05). Histologic cell type and stage of disease were defined for each patient. It was possible to calculate the growth rate of the primary tumor only in 68 of 150 patients, and it was recorded as doubling time. Evaluation of the skin test reaction in each prognostic subgroup showed no statistically significant differences. The only statistically significant differences were found when each prognostic subgroup was compared with the control population according to the frequency of a negative response to the skin test, particularly in stage III M1 (p less than 0.05) and stage III M0 (p less than 0.02). The delayed cutaneous hypersensitivity studied with recall antigen stimulation was mainly correlated with the stage of disease, and it should not be considered as an independent prognostic factor.