This study investigated the influence of a three-week sojourn on the island of Norderney on the lymphocyte subpopulations in the peripheral blood of patients with exogenous allergic bronchial asthma. For this purpose, we examined 25 patients at the start of their sojourn at our clinic, and again three weeks later. Patients with chronic bronchitis served as a control group. During the three-week stay, a clinical improvement in obstructive ventilation disturbances was observed. After 21 days, the patients with bronchial asthma showed a significant increase in the OKT8 suppressor cells (22.5-26.6%), and a significant decrease in helper/suppressor ratio (2.7-2.1). In patients with chronic bronchitis, no changes in the T lymphocyte subpopulations were to be found. The difference in the immunological status between the two disease categories present at the start of the study was, therefore, eradicated by a specific and unspecific therapy.